Colon and Rectum 1

COLON AND RECTUM 1

FRIDAY, MAY 21, 2021 Kaplan-Meier tests. Results: Over the study period, 327 consecutive patients (median age: 69 (IQR: 60-76) years old; 201 - 61.5%- males) were included in the analysis. The Colon and Rectum 1 90.8% of lesions were resected in an en-bloc fashion. The rate of R0 resection was Poster 83.1% (217/261) and 44.0% (29/66) for standard and hybrid techniques, respectively. Submucosal invasion and piece-meal resection independently predicted R0 resec- ID: 3526203 tions. A total of 18 (5.5%) intra-procedural AEs (11 perforations and 7 bleedings) and 12 (3.7%) post-procedural AEs (2 perforations and 10 bleedings) occurred. The two EFFICACY AND SAFETY OF COLD SNARE POLYPECTOMY patients readmitted for a post procedural perforation were referred for surgery and (CSP) OF INTERMEDIATE SIZED COLORECTAL POLYPS were excluded from the follow-up analysis. Seventy-five out of 327 lesions (23.0%) 10 - 15 MM- A PROSPECTIVE OBSERVATIONAL resulted in CR neoplasia with submucosal invasion. Fifty-seven of them showed FEASIBILITY TRIAL (COLDSNAP-1) high-risk features of nodal involvement (non-curative resection) and were excluded from the follow-up analysis, which finally involved 268 patients. Eighteen adenoma Paul Rechberger*, Jörg D. Ulrich, Mohamed Abdelhafez, recurrences per 1,000 person- years (15 cases, 5.6%) were detected in a median Guido von Figura, Jeannine Bachmann, Johannes R. Wiessner, follow-up time of 36 months. Any recurrence was detected after the 12 months FU Alexander Herner, Tobias Lahmer, Veit Phillip, Ulrich Mayr, endoscopy. No carcinoma recurrences were observed. R1 resection and intra-pro- Bernhard Haller, Moritz Jesinghaus, Roland Schmid, Christoph Schlag cedural adverse events independently predicted recurrences. Conclusion: Colorectal Introduction: Cold Snare Polypectomy (CSP) has been gaining interest in recent ESD, especially with standard approach, is a safe and effective option for managing years and is already an integral part of guidelines for polyps <10mm in size. In colorectal neoplasia in a Western setting, with short and long-terms outcomes contrast to hot snare polypectomy (HSP), CSP doesn’t involve electrocautery and comparable to published Eastern series. Achieving en-bloc, R0 resections, avoiding less adverse events (AE) with comparable resection rates have been shown. How- intra-procedural adverse events might minimize the risk of adenoma recurrence. ever, little is known about the feasibility of CSP for colorectal polyps of 10 to 15 mm. Therefore, this study evaluates the efficacy and safety of CSP for these polyps. Goals and Methods: This ongoing prospective observational study investigates the feasibility and safety of CSP for adenomatous polyps and sessile serrated lesions (SSL) FRIDAY, MAY 21, 2021 10-15 mm. Suitable polyps are removed by CSP using a hybrid snare. In case of failure conversion to HSP with the same snare is allowed. The primary outcome is Colon and Rectum 1 the histological complete resection rate, determined by pathologically negative Poster margins of the specimen and no residues adenomatous material obtained from four biopsies of the resection site. Secondary outcomes are en-bloc resection rate, failure ID: 3521920 of CSP with conversion to HSP and immediate bleeding. Furthermore, the incidence of adverse events such as delayed bleeding and perforation are observed. Results: By CLINICOPATHOLOGICAL CHARACTERISTICS OF now a total of 24 patients with 40 polyps were included. The mean polyp size was SERRATED POLYPOSIS SYNDROME: RESULTS OF A 12.1 mm, 75% (30/40) of these polyps were adenomas and 25% (10/40) were SSL. MULTICENTER STUDY BY THE COLORECTAL SERRATED The histological complete resection rate by CSP was 83.3% (25/30). En-bloc resec- POLYPOSIS SYNDROME (SPS) STUDY GROUP IN JAPAN tion could be achieved in 60% (18/30). Primary CSP failed with 10 (25%) polyps most likely due to large amount of tissue within the snare. These polyps were succesfully Yasutsugu Shimohara*, Yuji Urabe, Shiro Oka, Takashi Hisabe, removed after conversion to HSP with the same snare. Immediate bleeding occurred Atsushi Yamada, Hiro-O Matsushita, Hirotsugu Sakamoto, Joichiro Horii, with 16 (53.3%) lesions, which were treated by hemoclips (2.13 Clips on average). Daisuke Watanabe, Hirotsugu Eda, Fumika Nakamura, No other adverse events were observed. Conclusion: CSP seems to be efficient and Hironori Yamamoto, Tetsuji Takayama, Takayuki Matsumoto, safe in removing 10 – 15 mm colorectal polyps. A hybrid snare seems to be particular Shinji Tanaka, Hideki Ishikawa advantageous for larger polyps as it allows immediate conversion to HSP if CSP Background and aim: Serrated polyposis syndrome (SPS) is one of the colorectal might fail. polyposis, characterized by the occurrence of multiple serrated lesions.SPS is known to have a higher risk of colorectal carcinoma (CRC). The aim of this study was to clarify the clinicopathological characteristics of SPS in Japan. Materials and methods: We investigated the clinicopathological characteristics in patients with SPS FRIDAY, MAY 21, 2021 accumulated through the "Multicenter Study on clinicopathological characteristics of SPS (UMIN 000032138)" by the Colorectal Serrated Polyposis Syndrome (SPS) Study Colon and Rectum 1 Group, which was donated by the Japanese Society of Gastroenterology (JSGE). In Poster this study, we diagnosed patients with SPS according to 2019 World Health Orga- nization (WHO) SPS diagnostic criteria as follows; I) 5 serrated lesions/polyps ID: 3523472 proximal to the rectum, all being 5mm in size, with at least 2 being 10mm in size; and II) >20 serrated lesions/polyps of any size distributed throughout the large LONG-TERM OUTCOMES OF WESTERN-BASED bowel, with 5 being proximal to the rectum. Results: A total of 94 patients were ENDOSCOPIC SUBMUCOSAL DISSECTION FOR diagnosed with SPS at 9 institutes during a period from January 2001 until December COLORECTAL LESIONS 2017. The median (range) number of resected lesions per apatient was 6 (085). Maselli Roberta, Marco Spadaccini*, Paul J. Belletrutti, The median age at the diagnosis of SPS was 65 years (2285), 54 patients (57.4%) were male, and 17 patients (18.1%) had a history of CRC. Eighty-seven patients Piera Alessia Galtieri, Simona Attardo, Silvia Carrara, Alessandro Fugazza, fi Elisa Chiara Ferrara, Gaia Pellegatta, Andrea A. Anderloni, andrea iannone, (92.6%) satis ed the WHO diagnostic criteria I and 16 (17.0%) criteria II. Nine patients (9.6%) simultaneously satisfied criteria I and II. Among the overall 1689 polyps Cesare Hassan, Alessandro Repici Found in the patients, 926 lesions were resected. The pathological findings of the fi Background & aims: In Asian countries, the safety and ef cacy of endoscopic 926 resected lesions were as follows; 387sessile serrated lesions, 252 hyperplastic submucosal dissection(ESD) is well-established for the minimally invasive treatment polyps, 245 tubular adenomas, 13 traditional serrated adenomas, 18 Tis carcinomas, of colorectal (CR) neoplasia. Favorable long-term outcomes have been reported in 4 T1 carcinomas, and 7 advanced carcinomas. In twenty-eight of 32 patients with term of adenoma recurrence. The role of ESD for CR lesions in Western CRC, CRCs were detected at the index colonoscopy. Ten CRCs (7 Tis carcinomas, 2 communities is unclear and its adoption is still limited. This may be attributed to the T1 carcinomas, and 1 advanced carcinoma) were found during surveillance colo- disappointing technical outcomes in preliminary studies, along with the lack of long- noscopy. Two patients underwent surgery, with one of whom died of primary cancer term data coming from Western centers. The aim of this study is to assess the long- 60 months after the surgery. Of the 32 patients with CRC, 27 patients (84%) satisfied term outcomes of a large cohort of patients treated with colorectal ESD in a tertiary diagnostic criteria I, 2 patients (6.3%) diagnostic criteria II, and 3 patients (9.4%) Western center. Methods: Between February 2011 and November 2019, a retro- diagnostic criteria I and II. The prevalence of CRC was higher in patients who spective analysis of a prospectively maintained database was conducted on patients satisfied diagnostic criteria I than in those who satisfied diagnostic criteria II. treated by ESD for colorectal lesions at Humanitas Research Hospital in Milan, Italy. Conclusion: Of the 94 SPS patients who satisfied WHO diagnostic criteria, 32 pa- The primary outcome considered for this study was the recurrence rate. Secondary tients (34%) had CRCs. Patients with SPS have a high risk of CRCs and should un- outcomes were en-bloc, and R0 resection rates, procedural time, adverse events, and dergo surveillance colonoscopy. need for surgery. The curative resection rate was assessed for submucosal invasive lesions. Statistical analysis included descriptive statistics, Chi square and

AB74 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

FRIDAY, MAY 21, 2021 was attempted or achieved in 90 (42.5%) cases; 58 (27.4%) were resected en bloc and 29 (13.7%) in piecemeal fashion. Endoscopic mucosal resection was used in 29 Colon and Rectum 1 (23.8%) cases. Average polyp size was 2.7cm (s.d. 1.04). Referral patterns were: 102 Poster (48.1%) to TE, 17 (8.1%) to surgery, and 2 (0.9%) to TE plus surgery or other; 90 (42.5%) were not referred and continued follow-up with general GI. Polyp features fi ID: 3522946 signi cantly associated with referral to TE were large size, ileocecal valve location, and flat morphology (all p<0.01). Concern for malignancy was associated with EC-V (ENDOCYTOSCOPIC VASCULAR) CLASSIFICATION referral to surgery (p<0.01). At the end of the 3-year follow-up period, there were no IS USEFUL FOR NOT ONLY QUALITATIVE DIAGNOSIS statistically significant differences in incidence of HRN, adenocarcinoma, or death by BUT ALSO PATHOLOGICAL DIAGNOSIS referral type (Table 2). Conclusions: More patients with colorectal polyps 2cm Shinei Kudo*, Miyuki Kaneshiro, Masashi Misawa, Kenichi Mochizuki, were referred to therapeutic endoscopy than surgery without significant differences fl Hiroki Nakamura, Yuta Kouyama, Tomoyuki Ishigaki, Katsuro Ichimasa, in 3-year clinical outcomes. Polyps with large size, ileocecal valve location, and at morphology were more likely referred to therapeutic endoscopy while polyps with Shingo Matsudaira, Naoya Toyoshima, Yuichi Mori, Noriyuki Ogata, concern for malignancy were more likely referred to surgery. Future studies should Toyoki Kudo, Tomokazu Hisayuki, Takemasa Hayashi, evaluate longitudinal clinical outcomes by referral pattern and procedural manage- Kunihiko Wakamura, Hideyuki Miyachi, Toshiyuki Baba, Fumio Ishida ment for larger cohorts of patients with colorectal polyps 2cm. Backgrounds and Aims: Endocytoscopy (EC) is a kind of contact type endoscope that allows in vivo, real-time cellular observation with 520-times magnification, launched since 2019. Thus far, narrow-band imaging (NBI) could make it possible to analyze the surface microvessels of colorectal lesions for differentiating neoplasms from non-neoplasms and for predicting the histopathological diagnosis. EC combined with NBI (EC-NBI) enables in vivo observation of blood vessels in more detail compared to conventional magnification power. The aim of this study was to validate the evidence whether the observation of surface microvessels using EC-NBI was useful in predicting the histopathology of colorectal lesions. Methods: In this study, 622 patients who underwent complete colonoscopy and endoscopic or surgical treatment between April 2006 and December 2019. A total of 997 lesions (118 Non- neoplastic polyps, 640 adenomas, 77 intramucosal cancer(M), 21 slightly invasive submucosal cancer (SMs) and 141 massively invasive submucosal cancer(SMm)) were retrospectively evaluated. We used the Kudo classification for the degree of submucosal invasion. SMs cancer without vessel permeation does not metastasize. In contrast, SMm lesions show a substantial proportion (w10%) of lymph node metastasis. We named the ultra-magnified microvessel findings as EC-V classification and classified into the following 3 groups: EC-V1, the surface microvessels were very fine or obscure; EC-V2, the surface microvessels were clearly seen and showed a regular vessel network, and their caliber and arrangement were uniform; and EC-V3, the microvessels were thick, and their caliber and arrangement were non-homoge- neous. Corresponding histopathology among these classifications were as follows; EC-V1 corresponds to hyperplastic, EC-V2 corresponds to adenoma and EC-V3 corresponds to SMm. Result: The sensitivity, specificity and accuracy of EC-V1 for diagnosis of hyperplastic polyp were 87.2%, 98.6% and 97.3%, respectively. Secondly the sensitivity, specificity and accuracy of EC-V2 for diagnosis of adenoma or M or SMs were 97.2%, 84.6% and 93.9%, respectively. Similarly the sensitivity, specificity and accuracy of EC-V3 for diagnosis of SMm were 82.3%, 98.9% and 96.6%, respectively. Conclusion: EC-V classification was useful for predicting the histopathology of colorectal lesions.

FRIDAY, MAY 21, 2021 Colon and Rectum 1 Poster

ID: 3523799 REFERRAL PATTERNS, POLYP FEATURES, AND CLINICAL OUTCOMES FOR COLORECTAL POLYPS ≥ 2CMINA LARGE TERTIARY CARE HEALTH SYSTEM Bao Sean Nguyen*, Camille Soroudi, Allen R. Yu, Brandon Smith, Madeline Treasure, Sartajdeep Kahlon, Stephen Kim, Adarsh M. Thaker, Liu Yang, Folasade (Fola) P. May Introduction: Although 2020 US Multi-Society Task Force guidelines recommend endoscopic removal of colorectal polyps 2cm by an experienced gastroenterolo- gist, considerable heterogeneity exists in the management of these patients. We examined referral patterns, polyp features, and clinical outcomes for patients with colorectal polyps 2cm at a tertiary care health system. Methods: We used an internally developed natural language processing algorithm to identify all patients diagnosed with at least one colorectal polyp 2cm on index colonoscopy between 1/ 1/2013 and 12/31/2017 across 5 endoscopy units within a large health system. We excluded patients with a history of colorectal cancer (CRC), inﬂammatory bowel disease, or familial polyposis syndromes. We performed manual chart review to conﬁrm large polyp status and collect patient data on demographic and clinical factors, referrals, procedural management, and clinical and histologic outcomes. The primary outcome was the proportion of patients referred to therapeutic endoscopy (TE), surgery, TE plus surgery, other, or who received care only with general gastroenterology (GI). Secondary outcomes included polyp features and 3-year clinical outcomes (high-risk neoplasia (HRN), adenocarcinoma, and death) associated with each type of referral. We used chi-square and Fisher’s exact tests to examine associations between referral pattern, polyp features, and clinical outcomes. Results: The study cohort included 212 patients who underwent index colonoscopy with general GI (Table 1). In index colonoscopies, endoscopic resection

www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB75 Abstracts

UCS vs. hot snare techniques for 10mm non-peduncuated, non-bulky colorectal lesions to assess efﬁcacy, adverse outcomes and costs is indicated.

FRIDAY, MAY 21, 2021 Colon and Rectum 1 Poster

ID: 3520297 UNDERWATER COLD SNARING LARGE (≥10MM) NON- PEDUNCULATED, NON-BULKY COLORECTAL LESIONS IS FEASIBLE WITH HIGH EN BLOC RESECTION RATES Andrew W. Yen*, Joseph W. Leung, Felix W. Leung Background: Adverse events are rare with cold snare resection, but cold techniques are mainly reported for 9mm lesions out of concern for incomplete resection or inability to remove larger lesions en bloc [Dig Endosc 2017;29:594]. In a non-distended, water-filled lumen (gas excluded), colorectal lesions are not stretched and are more compact. Complete capture by snare and en bloc resection underwater with electrocautery, even of large lesions appears to be possible [GIE 2015;81:713]. Achieving an adequate depth of resection with underwater snaring compared to polypectomy in a gas distended colon has also been observed and is another potential advantage [Dig Endosc 2019;31:662]. Aims: We assessed the feasibility of underwater cold snare (UCS) resection of 10mm non-pedunculated, non-bulky FRIDAY, MAY 21, 2021 (5mm elevation) colorectal lesions in a VA endoscopy unit. Methods: Analysis was Colon and Rectum 1 performed on an observational cohort with lesions removed by UCS without submucosal injection (SI) during routine outpatient colonoscopy from 1/2016 to 11/ Poster 2020. Pedunculated and/or bulky lesions where mechanical transection of tissue by cold techniques can be limited, and patients enrolled in other clinical trials, were not ID: 3526923 included. A single endoscopist performed procedures using a thin wire cold or ENDOSCOPIC MUCOSAL RESECTION (EMR) VS. hybrid snare. Attempts were made to completely remove lesions en bloc. Results: Fifty-three lesions (mean 15.8mm [SD 6.9]; range 10-35mm) were removed by UCS ENDOSCOPIC SUBMUCOSAL DISSECTION (ESD) FOR from 44 patients. Image 1 shows patient demographics and lesion characteristics. LARGE RECTAL POLYPS Image 2 compares UCS to a cohort of 10mm non-pedunculated lesions removed Fnu Chesta*, Anmol Singh, Meher Oberoi, Prabh G. Singh, by underwater hot snare without SI and conventional submucosal injection, lift and Ganeev Bhangoo, Kevin T. Behm, Louis M. Wong Kee Song, ’ hot snare (EMR) techniques from the author s previously published RCT [GIE 2020 Navtej S. Buttar 91:643] and reports from the literature. Significantly more lesions were successfully Z Background and Aims: Endoscopic mucosal resection (EMR) allows for faster resected en bloc by UCS (84.9% [45/53]; p 0.03) compared to conventional EMR resection and shorter procedure duration while endoscopic submucosal dissection (60.4% [32/50]) with no significant immediate adverse events. Results were driven Z (ESD) facilitates en bloc resection of large/complex polyps for more accurate by high en bloc resection rates for 10-19mm lesions (97.3% [36/37]; p 0.01). histopathological evaluation. Our aim was to compare the efficacy and safety of EMR Omission of SI and forgoing prophylactic clipping of post resection sites conserved and ESD for rectal polyps 20 mm. Methods: Patients referred for large (>20 mm) expenses and did not result in increased short-term adverse outcomes. Limitations: rectal polyp resection between 01/2011 and 12/2019 were identified from our Retrospective study; single unblinded endoscopist; VA patients. Conclusion: UCS of endoscopy database using Advanced Cohort Explorer. All EMR and ESD were per- 10mm non-peduncuated, non-bulky colorectal lesions is feasible with high en bloc fi formed by two experienced endoscopists. Data were abstracted for patient demo- resection rates. No clinically signi cant short-term adverse outcomes were observed. graphics, polyp characteristics, procedural details, adverse events, and polyp Decreased resource utilization with avoidance of prophylactic clipping and SI, which residual/recurrence. Results: Out of 525 patients with large (nZ762) colorectal requires an injection needle and injectate solution, as well as fewer piecemeal re- polyps, 92 patients (97 rectal polyps) met inclusion criteria, of which 54 polyps were sections that require closer follow up, are also potential benefits. A RCT comparing

AB76 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts resected by EMR (49 patients) and 43 by ESD (43 patients). Mean polyp size was 32 The aim of this study was to identify the main risk factors for stenosis and symptoms mm (range 2070 mm) and 38 mm (range 3084 mm) for EMR and ESD, respec- after ESD of large rectum lesions and their treatment. Materials and Methods: We tively (pZNS). Fewer polyps were at the dentate line in the EMR group compared to retrospectively analyzed all patients identified from a prospectively maintained the ESD group (7.4 vs 41.8%, p<0.05). Endoscopic clips were used more frequently database of patients submitted to ESD for rectal lesions between July 2010 and in the EMR group compared to the ESD group (p<0.05). Four (8.1%) patients in the January 2020. Patients were followed in regular appointments and in scheduled EMR group underwent surgery for adenocarcinoma in the resected specimens and surveillance exams. Primary outcomes were post-ESD stenosis – total or partial. Total post-surgical specimens revealed no residual adenocarcinoma in two. Additionally, stenosis was defined when the rectal lumen became too narrow to allow passage of a two patients in the EMR group elected surgery for incomplete resection. Three standard 12.8 mm diameter endoscope. Partial post-ESD stenosis was defined when (6.9%) patients in ESD group underwent surgery for invasive adenocarcinoma, with the rectal lumen became narrow enough to difficult the passage of a standard residual malignancy found in one. One additional patient required surgery in the endoscope, but not too narrow to impossibilities the passage. Secondary outcomes ESD group due to perforation. Procedure related delayed bleeding was encountered were the presence of symptoms related to stenosis and the respective treatment in one (2%) patient in the EMR group (managed by clip placement) and one (2.3%) when necessary. Statistical analyses were performed using SPSS software. Results: A patient in the ESD group (managed by hemostatic forceps). The rate of delayed total of 98 resections were performed in the period (median size 68 mm). Thirteen adverse events rates trended higher for ESD relative to EMR (20.9% vs. 10.2%, were excluded from analysis: 8 due to complications or deep invasion, 4 were not pZNS). Transmural burn syndrome was observed in more patients post ESD than curative and 1 discontinued follow up. In a total of 85 patients analyzed, 69 did not post EMR (9.3% vs 0%, pZ0.04). In the ESD group, three patients had delayed present stenosis, 9 presented total stenosis and the other 7 partial stenosis (median bleeding and one had perforation requiring endoscopic suturing. In the EMR group, size 108 mm, p<0.05). The size of the lesion and the degree of circumferential three patients had delayed bleeding and two had microperforations managed mucosal defect were significative different between the two groups. However, only conservatively. Two (4.7%) patients in the ESD group and three (6.1%) in EMR the grade of mucosal defect greater than 90% persisted as a risk factor for stenosis group had residual/recurrent lesions that were all managed endoscopically. after multivariated analyses (table 1).7 patients with stenosis presented severe Conclusion: Both EMR and ESD are safe and effective for the resection of large rectal symptoms and were treated with consecutive dilation sessions (table 2). Total ste- polyps. However, ESD patients were more likely to have complex polyps abutting nosis and the distance from anal verge shorter than 5 cm showed significative dif- the dentate line. To overcome selection bias, a randomized trial of EMR vs ESD for ference between the patients with or without symptoms (table 1). Conclusions: A rectal polyps is warranted. large lesion with mucosal defect greater than 90% is the main isolated risk factor for stenosis after submucosal dissection of large rectum lesions. Total stenosis after procedure and distance to anal board shorter than 5 cm are more likely to present symptoms. Those patients require special attention and earlier return.

Table 1. Comparsion between with and without stenosis groups and between with and without symptoms groups

Outcomes of EMR vs ESD for large rectal polyps Table 2. Characteristics of patients and treatments for stenosis

FRIDAY, MAY 21, 2021 Colon and Rectum 1 FRIDAY, MAY 21, 2021 Poster Colon and Rectum 1 Poster ID: 3526513 RISK FACTORS FOR STENOSIS AFTER ENDOSCOPIC ID: 3524934 SUBMUCOSAL DISSECTION OF LARGE LESIONS OF THE MALIGNANT LARGE BOWEL OBSTRUCTION AND RECTUM COLONIC STENTING AS SAFE BRIDGE TO SURGERY - A Daniel T. Rezende*, Fabio S. Kawaguti, Bruno Martins, CLINICAL AUDIT OF EFFICACY AND SAFETY IN A Adriana V. Safatle-Ribeiro, Caio Sergio R. Nahas, Carlos F. Marques, TERTIARY CENTRE Amanda A. Pombo, alisson L. Santos, Oddone F. Braghiroli, Garrett Kang*, James Weiquan Li, Andrew Kwek, Eng Kiong Teo, Ulysses Ribeiro, Sergio C. Nahas, Fauze Maluf-Filho Kwong Ming Fock, Tiing Leong Ang Background: The development of stenosis in the rectum after endoscopic submuco- Introduction: Approximately 8-15% of colorectal cancers (CRC) present with acute sal dissection (ESD) is one of the most frequently delayed complication, ranging malignant large bowel obstruction (MBO). Emergency surgery in this setting is from 4.2 to 19.7 % of the resections of large rectal lesions. Circumferential mucosal associated with high post-operative mortality and morbidity. Self-expandable metal defect greater than 90% seems to be only independent predictor of stenosis. stent (SEMS) in MBO has been used as bridge-to-surgery (BTS) and as destination Morphology and size have not shown relation with the occurrence of strictures. therapy for palliation in unresectable tumours. We aimed to conduct a clinical audit However, due to the small number of cases reported, the factors that really pre- to review the safety and efficacy of SEMS placement in patients with MBO in our dispose to stenosis after ESD of rectal lesions may be not yet fully understood. Aim: www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB77 Abstracts institution. Methods: Review of data was conducted on a prospectively maintained FRIDAY, MAY 21, 2021 electronic patient database in a tertiary referral centre in Singapore. All consecutive patients undergoing SEMS insertion for MBO were included in the audit. Technical Colon and Rectum 1 success was defined as successful deployment of the SEMS across the malignant Poster stricture without complications. Clinical success was defined as colonic decom- pression within 24h without requiring further surgical intervention. Rates of com- ID: 3524655 plications were studied. Median time to surgery, types of surgery and rates of recurrence of our cohort were recorded. Results: 92 patients underwent emergent REFERRAL PATTERNS FOR ENDOSCOPIC RESECTION SEMS placement for MBO from September 2013 to November 2020. Mean age of our OF LARGE COLON POLYPS AMONG ACADEMIC VS. patients was 67.6 years ( 14.0 years), 48/92 (52%) were male. Obstruction was COMMUNITY-BASED GASTROENTEROLOGISTS: A fl predominantly distal to splenic exure: rectum (4/92, 4.3%), rectosigmoid (19/92, SINGLE ACADEMIC TERTIARY CARE CENTER 20.7%), sigmoid (34/92, 37.0%), descending (26/92, 28.3%) and transverse colon (9/ 92, 9.8%). Mean length of CRC was 4.2cm ( 2.1cm). Technical success was 94.6% EXPERIENCE (87/92) and clinical success was 94.3% (82 out of 87). Perforation occurred in 4/92 Philip Kozan*, Allen Yu, M. P. Fejleh, Alireza Sedarat, (4.3%) patients. Stent migration occurred in 4/92 ( 4.3%) of patients. Tumour V. Raman Muthusamy, Stephen Kim overgrowth occurred in 3/92 (3.3%%) of patients. There were no cases of bleeding. Introduction: Endoscopic mucosal resection (EMR) is a safe and cost-effective 60/92 (65.2%) of SEMS were inserted as BTS. Median time to surgery was 20 days method of removing large, benign colon polyps with a low risk of complications (range 2-57 days). 50/60 (83.3%) of patients underwent minimally invasive surgery and high rates of clinical success. As rates of colon polyps being referred for EMR (robotic-assisted 9/60, 15%; laparoscopic 41/60, 68.3%) while 10/60 (16.7%) under- continue to rise, it is important to recognize and understand trends in referral pat- went open surgery. Rate of primary anastomosis was 96.7% (58/60). 39 patients had terns for colon polyp EMR. Methods: A retrospective chart review was performed to follow-up for more than 1-year post-treatment (median 34 months). Local recur- identify patients who underwent an index colonoscopy with a colon polyp greater rence and distant metastasis was observed in 4/39 (10.3%) and 5/39 (12.8%), than or equal to 1 cm in size who were subsequently referred for colon polyp EMR respectively. Conclusion: SEMS insertion in acute MBO has high technical and with an interventional endoscopist at a single tertiary academic center over one clinical success rates. The main complications were perforation, stent migration and academic year (2018-2019). Our primary outcome was to determine if there was a tumour overgrowth. Majority of patients in our audit underwent minimally invasive difference in colon polyp size referred for EMR between general gastroenterologists surgery and primary anastomosis after successful BTS. from within the academic center and community-based gastroenterologists. Statis- tical analysis was performed with Welch’s t-test and Chi-square test. Results: In the study cohort, 267 total patients were referred for endoscopic mucosal resection of large colon polyps that were unable to be removed at index colonoscopy. Of the 173 FRIDAY, MAY 21, 2021 (64.8%) patients referred by gastroenterologists from within the academic institution, a total of 205 large colon polyps were identified and removed. Among the 94 Colon and Rectum 1 (35.2%) patients referred from community-based gastroenterology practices, a total Poster of 111 large colon polyps were identified and removed. There were no significant differences in the age, gender, and race of the patients in the two groups (Table 1). Gastroenterologists from community practices outside of the academic institution ID: 3520164 referred larger colon polyps than those who practiced within the academic health LONG-TERM PROGNOSIS AFTER ENDOSCOPIC system (27.315.2 cm v. 22.113.9 cm, p Z 0.003). In addition, academic gastro- SUBMUCOSAL DISSECTION FOR COLORECTAL TUMORS enterologists were more likely to refer colon polyps that were 15 mm (nZ86 vs. IN PATIENTS AGED OVER 80 YEARS nZ27, pZ0.001) as compared to community-based gastroenterologists (Table 2). Tomoyuki Nishimura*, Shiro Oka, Yuki Kamigaichi, Hirosato Tamari, Conclusion: Community-based gastroenterologists refer larger colon polyps than academic gastroenterologists for endoscopic mucosal resection. More specifically, the Yasutsugu Shimohara, Yuki Okamoto, Katsuaki Inagaki, Kenta Matsumoto, community-based gastroenterologists are less likely to refer colon polyps 15 mm Hidenori Tanaka, Ken Yamashita, Yuki Ninomiya, Yasuhiko Kitadai, in size. These findings warrant further investigation in emerging referral patterns for Shinji Tanaka colon polyp EMR. Background: In Japan, endoscopic submucosal dissection (ESD) has been standardized for large colorectal tumors, however its validity in the elderly population is unclear. We aimed to evaluate the safety and efficacy of ESD for colorectal tumors in elderly patients aged over 80 years. Methods: Colorectal ESD was performed on 178 tumors in 165 consecutive patients aged over 80 years between December 2008 and December 2018. The patients who could be prepared for colonoscopy with more than 1-L bowel cleansing agent were indicated for ESD. We retrospectively evaluated the clinicopathological characteristics and clinical outcomes of colorectal ESD and assessed the prognosis of 160 patients followed up for more than 12 months. Results: The mean patient age was 83.7+3.1 years. The number of patients with comorbidities was 100 (62.5%). The most common comorbidity was hypertension (52%), and the second one was cardiac disease (25%). Among all patients, 106 (64.2%) were categorized as the American Society of Anesthesiologists classification of physical status (ASA-PS) class 1 or 2, and 59 (35.8%) as class 3. The mean procedure time was 97.779.3 minutes. The rate of histological en bloc resection was 93.8% (167/178). Delayed bleeding in 11 cases (6.2%) and perforation in 7 cases (3.9%) were treated conservatively. The 5-year survival rate was 89.9% (mean follow- up time: 35.3+27.5 months). A total of 25 deaths during prognostic observation were noted. Primary cancer death accounted for one patient who required absolute surgery indication due to a positive vertical margin in ESD specimens. The patient refused additional surgery, and recurrence occurred, comprising lung and liver metastasis, within 8 months after ESD. Overall survival rates were significantly lower in the non-curative resection group that did not undergo additional surgery than in the curative resection group (PZ0.0152) and non-curative group that underwent additional surgery (PZ0.0259). Overall survival rates were higher for ASA-PS class 1 or 2 patients than for class 3 patients (PZ0.0105). Metachronous tumors (>5 mm) developed in 9.4% of patients. Conclusions: ESD for colorectal tumors in patients aged over 80 years is safe. Colorectal cancer-associated deaths were prevented regardless of ASA-PS although comorbidities pose a high risk of poor prognosis.

AB78 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

FRIDAY, MAY 21, 2021 Colon and Rectum 1 Poster

ID: 3521534 MAJORITY OF INDIVIDUALS WHO HAVE DECLINED COLONOSCOPY AND STOOL TEST ARE WILLING TO UNDERGO BLOOD TEST FOR CRC SCREENING Yongyan Cui*, Anika Zaman, Anne M. Kaminsky, Gabriel Castillo, Craig T. Tenner, Scott E. Sherman, Jason A. Dominitz, Peter S. Liang Introduction: One-third of Americans between age 50 and 75 years are not up to date with colorectal cancer (CRC) screening. Barriers to colonoscopy and stool- based testing have led to ongoing interest in blood-based screening tests. As part of a clinical trial assessing the impact of offering a Septin9 blood test for CRC screening in individuals who’ve previously declined colonoscopy and fecal immunochemical testing (FIT), we conducted a questionnaire to understand patient perspectives on different CRC screening methods. Methods: Patients receiving care at a VA medical center who were aged 50 to 75 years, at average risk for CRC, not up to date with screening, and with documented refusal to screening in the prior 6 months were sent a questionnaire as part of the invitation to join the trial. Questionnaire items included demographics, health status, medical history, and perspectives on different CRC screening modalities. Questionnaires were either directly returned by mail or completed in-person or over the phone with the help of research staff. Results: Of 404 questionnaires that were mailed, 95 (23.5%) were completed. The majority of survey participants were aged 61 to 75 years (78.7%), 48.4% were White, and 38.5% were Black. The highest educational level attained was high school in 48.4%. Self- reported health was good or very good in 68.4%. Most rated their risk of developing CRC as either low or below average (76.7%), but 23.2% knew someone who was diagnosed with CRC. Half (52.7%) had previously undergone colonoscopy and 41.8% had a prior stool test. Perceptions about barrier and facilitators for colonoscopy and stool testing are shown in Table 1. Notably, 20.0% and 30.9% of individuals responded they were not offered colonoscopy and FIT in the past 6 months, despite documentation to the contrary. The majority of patients (88.6%) indicated that they would take a blood test for CRC screening. Of those who said they would take the blood test, the perceived advantages over colonoscopy and stool test included convenience (59.7%), being accustomed to receiving blood tests (40.3%), and no requirement for special preparation (38.9%, Figure 1). Only 18.1% believed that a FRIDAY, MAY 21, 2021 blood test had an advantage in terms of accuracy. No significant association was observed between demographics, health status, or screening history and willingness Colon and Rectum 1 to take a blood test, although sample size was limited. Conclusions: Among patients Poster who have previously declined colonoscopy and FIT, 89% reported willingness to take a blood test for CRC screening. These data indicate that a blood-based test offers an opportunity to substantially improve overall screening uptake. Given a ID: 3526661 substantial proportion of individuals who do not recall being recently offered colo- SELF-EXPANDING METAL STENTS FOR THE TREATMENT noscopy and FIT, these first-line tests should be re-offered before discussing alter- OF MALIGNANT COLON OBSTRUCTION CAUSED BY native tests. EXTRA-COLONIC VERSUS INTRA-COLONIC MALIGNANCY – A META-ANALYTIC COMPARISON OF SAFETY AND EFFICACY Faisal S. Ali*, Mohammed R. Gandam, Samreen Khuwaja, Nivedita Sundararajan, Samrah I. Siddiqui, Syeda Naqvi, Sushovan Guha, Nirav Thosani, Maryam R. Hussain, Shahrooz Rashtak, Srinivas Ramireddy, Ricardo Badillo, Tomas DaVee Introduction: The relative utility of self-expanding metal stent (SEMS) insertion for malignant colon obstruction (MCO) due to extra-colonic malignancy (ECM) versus intra-colonic malignancy (ICM) is understudied. Methods: A comprehensive search of Medline (Ovid) and Embase (Ovid) was performed from inception-October 2020. All studies were screened by two authors to identify reports of safety and efficacy of www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB79 Abstracts

SEMS insertion for the treatment of MCO by ECM and ICM. A meta-analysis of proportions, comparative meta-analysis to compute odds ratios (OR) and mean differences (MD) with 95% confidence intervals (CIs) were performed. Results: Six non-randomized studies enrolling 430 ECM and 439 ICM patients were included, 48% (40-57%) and 62% (58-67%) of patients in the ECM and ICM groups were male. ECM patients were younger than ICM (57.73 vs 63: Table 1; MD -4.44; -8.59, -0.30; I2 79.01%: Table 2). Most obstructions were in the rectosigmoid colon in both ECM and ICM groups. The pooled technical success (TS) of SEMS was similar: 89% (83- 96%) in the ECM and 96% (94-98%) in the ICM groups (OR 0.39; 0.10-1.60; I2 64.66%; Table 2). The clinical success (CS) of SEMS was also similar: 74% (63-86%) in the ECM and 89% (86-92%) in the ICM groups (OR 0.63; 0.13-3.11; I2 93.19%). Adverse event rate was 29% (16-42%) in the ECM and 15% (12-19%) in the ICM group (OR 1.39; 0.54-3.60; I2 83.25%). The most common AE was recurrent obstruction due to tumor in-growth in both ECM (49%; 36-62%) and ICM (53%; 39- 66%) groups, followed by SEMS migration (19% (2-35%) in ECM, 22% (13-30%) in ICM). Endoscopic reintervention rate was 34% (22-46%) in the ECM and 42% (30- 54%) in the ICM group (OR 0.53; 0.19-1.50; I2 29.21%). Surgical intervention rate post-SEMS placement was 17% (12-21%) in the ECM and 6% (3-9%) in the ICM group (OR 2.76; 0.56-13.58; I2 85.73%). There was no significant difference in stent patency Forest Plots of Techincal Success, Clinical Success, Adverse Events, and (MD -9.97 days; -59.73, 39.79; I2 98.71%) and overall survival (OS) between the two Overall Survival - SEMS for the Treatment of Malignant Colon Obstruction groups (MD -120 days; -276.48, 36.27; I2 99.52%). The mean duration of stent patency was 138.45 days (132.92-143.99) in the ECM and 134.47 (132.26-136.69) in from Intra- and Extra-Colonic Malignancy the ICM group. The mean OS was 127.2 days (121.03-133.38) in the ECM and 177.17 days (170.75-183.60) in the ICM group. Conclusion: Clinical outcomes were comparable after endoscopic stent placement for treatment of both extracolonic and intracolonic malignant obstructions. Although the point estimate of technical and FRIDAY, MAY 21, 2021 clinical success weighed in favor of intracolonic obstructions, and the point esti- Colon and Rectum 1 mates of survival and adverse events weighed towards extracolonic obstructions, the confidence intervals were wide, diminishing potentially significant findings. The Poster heterogeneity of the data was significant. Future research is needed to further validate these findings. ID: 3521766 THE IMPACT OF COVID-19 ON TIMELY SURVEILLANCE COLONOSCOPIES IN SOUTH AUSTRALIA Molla M. Wassie*, Madelyn Agaciak, Charles Cock, Graeme P. Young, Erin L. Symonds Background: The COVID-19 pandemic has affected all elective procedures, including colonoscopy, in hospitals worldwide. Delays in surveillance colonoscopies might increase the progression of cancer in people at increased risk for colorectal cancer. Limited colonoscopy capacity, as well as patient reluctance to attend hospital, could lead to colonoscopies not being completed within the appropriate time frame. This study aimed to determine the impact of COVID-19 on the number of colonoscopies performed, the magnitude of delay to surveillance colonoscopies, and whether the pandemic altered patient response to a recall letter for their surveillance colonoscopy in South Australia. Methods: This was a retrospective analysis of surveillance data during the 3 months (April-June 2020) when colonoscopy services were most affected by COVID-19 in South Australia, compared to the three months in 2019 (pre-COVID-19). Data on when surveillance colonoscopies were recommended, and responses to colonoscopy recall letters, were obtained from the public hospital surveillance program. Surveillance colonoscopy was defined as delayed if the colonoscopy was done more than 3 months after the due date based on national recommended surveillance intervals. The c2 test was used to compare percentages between groups (P<0.05 considered statistically significant). Results: During the audited period in 2020, the total number of colonoscopies completed decreased by 51.1% (nZ569), compared to the same months in 2019 (nZ1164). The proportion of urgent category (category 1) colonoscopy procedures increased from 66.8% (746/ 1117) in 2019 to 86.2% (461/535) in 2020 (p<0.001), accompanied by a decrease in the number of surveillance colonoscopies done from 371 to 74 (p<0.001). Of 632 surveillance colonoscopies due during the audited period, the number of delayed surveillance colonoscopies increased from 49.8% (162/325) in 2019 to 62.9% (193/ 307) in 2020 (p<0.001). For the patients 75y sent a letter to consider another colonoscopy, in 2020 there were significantly more non-responders (51.6%) compared to that observed in 2019 (23.1%, pZ0.013) however, for responders there was no difference in the proportion requesting booking. No differences were observed in the responses of the patients <75y (p>0.05). Conclusions: Significant reductions and delays in surveillance colonoscopies were seen during the COVID-19 pandemic in South Australia, despite a very limited pandemic in this geographic location. This occurred due to a reduction in the total number of non-urgent pro- Table 1 & 2. Meta-Analytic Proportions and Comparison of SEMS for the cedures, rather than patient reluctance to have their procedure. These effects are Treatment of Malignant Colon Obstruction from Intra- and Extra-Colonic likely to be much larger in areas affected more by the pandemic. Thus, planning for Malignancy post COVID-19 colonoscopy triage and capacity is required to avoid cancer progression in elevated-risk patients due to delays in surveillance colonoscopies.

AB80 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

FRIDAY, MAY 21, 2021 multiple studies suggest that DSI in absence of other histologic high-risk features might not be a strong predictor for LNM. We conducted a systematic review and Colon and Rectum 1 meta-analysis to determine whether DSI is an independent risk factor for LNM in T1 Lecture CRC. Methods: A systematic search in MEDLINE, EMBASE and Cochrane Library was performed from inception to July 2020 (PROSPERO: CRD42020145938). To establish ID: 3525121 the risk of DSI for LNM in univariate analysis, all suitable studies were included in meta-analysis. To determine whether DSI (1000mm or sm2-3) was an independent EFFICACY OF COLD SNARE ENDOSCOPIC MUCOSAL risk factor in relation to other accepted histological risk factors such as poor dif- RESECTION FOR SESSILE SERRATED LESIONS ferentiation (PD), lymphovascular invasion (LVI) and/or high-grade tumor budding COMPARED TO ADENOMATOUS LESIONS (TB), studies were eligible if 1) DSI was described as the only present high-risk factor Matthew Mickenbecker*, Jeevithan Sabanathan or 2) the above-mentioned four main histological risk factors were simultaneously Background and Aim: Endoscopic mucosal resection (EMR) with a cold snare is included in a multivariate analysis. Authors were contacted to provide multivariate gaining increasing acceptance as an effective therapy for large laterally spreading analysis or raw patient data when required. Meta-analysis was performed using a fi lesions in the colon. The cold snare technique offers a favorable risk profile, with low random-effects model and reported as pooled odds ratio (OR) with 95% con dence rates of bleeding, perforation, and post-procedure pain compared to the more interval (CI). Results: 59 studies were included comprising in total 19,793 patients. widely used hot snare EMR technique. While there is increasing acceptance of cold Overall, LNM was present in 11.2%. The number of cases with LNM in univariate fi snare EMR for the removal of medium (10-19mm) and large (20mm) sessile analysis, analyzed in all included studies, was signi cantly higher in the group with fi serrated lesions (SSLs), concerns remain about its suitability for the removal of DSI (1,903/12,432; 15.3%) compared to group with super cial invasion (228/4,343; similar sized adenomas. We aimed to study the differences in safety and efficacy of 5.2%) (OR 2.73; 95%CI 2.19-3.41). Seven studies (3303 patients) described presence cold snare EMR for SSLs as compared to adenomas at our institution. of DSI in absence of all other high-risk factors. The overall rate for LNM was 2.7% Z Methods: Data was collected retrospectively for EMR procedures of Paris IIa SSLs (n 26/977) resulting in a pooled incidence rate of 0.03 (95%CI 0.02-0.05). Seven and adenomas performed at a single centre between 01/02/2018 and 31/05/2020. studies (3515 patients) included DSI in a multivariate analysis in relation to the other The Provation endoscopy reporting program was used to source size, morphology, three risk factors. DSI was the weakest predictor for LNM with an OR of 1.94 (95%CI 1.05 – 3.57), compared to PD (OR 2.71; 95%CI 1.70 – 4.32), TB (OR 2.59; 95%CI 1.85 method of resection, and recurrence data. Complications were captured through a – – review of medical records that included a one-month follow-up phone call. Results: 3.62) and LVI (OR 3.52; 95%CI 2.01 6.17). Discussion: Our meta-analysis dem- A total of one hundred forty-two eligible EMR procedures were performed over the onstrates that DSI is an independent, but weak predictor for LNM. In DSI cancers, study period (Table 1). The SSLs and adenomas were similarly located throughout the rate of LNM is low (2.7%) in the absence of other risk factors. In light of the the colon. One hundred nineteen patients had completed their six-month surveil- expanding spectrum of endoscopic resection methods and overtreatment by surgery lance colonoscopy (SC1) and forty-six their eighteen-month surveillance (SC2). The for many patients with T1 CRC, DSI should be reconsidered as strong indicator for overall recurrence rate at SC1 was considerably lower in the SSL group (3.2% vs oncologic surgery. 14.0%, OR 0.20, P 0.05). The difference was most appreciable in lesions 20mm or larger (3.1% vs 18.4%, OR 0.14, P 0.08). Recurrence was able to be treated endoscopically in all cases. There were no complications reported in either group. Conclusion: Our study demonstrates both safety and efficacy of the cold snare tech- FRIDAY, MAY 21, 2021jSATURDAY, MAY 22, 2021 nique for medium and large SSLs, while raising concerns about efficacy, but not Colon and Rectum 1 safety, for similarly sized adenomas. It is reassuring that recurrence was able to be j treated endoscopically in all cases. Considering this and the impressive safety profile Lecture Lecture of the cold EMR technique, particularly in high risk patients, it may still have a place in the EMR of medium and large adenomas. Further research is required to un- ID: 3521647 derstand the reasons for this increased recurrence and to determine the optimal EFFECT OF CLIP CLOSURE ON OUTCOMES AFTER technique for cold snare EMR of adenomas. RESECTION OF LARGE SERRATED POLYPS: RESULTS FROM A RANDOMIZED TRIAL Seth Crockett*, Mouen A. Khashab, Douglas K. Rex, Ian S. Grimm, Matthew T. Moyer, Heiko Pohl Background: Serrated polyps, particularly sessile serrated lesions (SSL), are important colorectal cancer precursors. Endoscopic management of serrated polyps often differs from that of adenomatous polyps due to morphology and other specific endoscopic features. SSLs are most commonly located in the proximal colon, where post-polypectomy bleeding rates are higher. There is limited clinical trial evidence to guide best practices for resection of large serrated polyps. Methods: In a multicenter international trial, patients with large (20mm) non-pedunculated polyps removed via endoscopic mucosal resection (EMR) were randomized to either clipping of polypectomy defect or not. This analysis is limited to participants with study polyps that had serrated histology [SSL, hyperplastic polyps (HP), or traditional serrated adenomas (TSA)], comparing those randomized to clip vs. control group. The primary outcome was severe post-procedure bleeding within 30 days of colonoscopy. Secondary outcomes included risk of other serious adverse events, including perforation and post-polypectomy syndrome. Frequency of outcomes were compared between groups using Chi-squared tests. Two tailed p values less than 0.05 were considered statistically significant. Results: A total of 195 participants with 220 serrated study polyps were included in the study. Polyps included 198 SSLs, 14 TSAs, and 8 HPs. The mean age was 63 (SD 9.9), and 53.3% were female (Table 1). 39 (20%) participants used antithrombotic medications, including a higher propor- FRIDAY, MAY 21, 2021 tion in the control vs clip group (26% vs 14%, pZ0.038). Median size of serrated Colon and Rectum 1 polyps was 25mm (IQR 20, 30), and the polyps were predominantly located in the right colon (Table 2). 11% of participants had more than 1 qualifying study polyp. 99 Lecture were assigned to clip closure and 96 were assigned to control. Overall, 7 patients (3.6%) experienced post-procedure bleeding following resection of large serrated ID: 3521068 polyps. There was no difference in post-procedure bleeding rates between patients in the clip vs. control group (4.2% vs 3.0% respectively, pZ0.48). 2 out of 4 patients DEEP SUBMUCOSAL INVASION AS INDEPENDENT RISK in the control group with post-procedure bleeding used antithrombotic medica- FACTOR FOR LYMPH NODE METASTASIS IN T1 tions. 1 patient suffered a perforation and 1 patient had post-polypectomy syn- COLORECTAL CANCER: A SYSTEMATIC REVIEW AND drome, both in the control group. Conclusion: Results from this clinical trial META-ANALYSIS demonstrate that the post-procedure bleeding rate for large (20mm) serrated fi Liselotte W. Zwager, Barbara A. Bastiaansen*, Nahid Mostafavi, polyps removed via EMR is low, and that there was not a clear bene t of prophylactic clipping of the polypectomy defect in this group. Although small sample size is a Roel Hompes, Valeria Barresi, Katsuro Ichimasa, Hiroshi Kawachi, limitation, this study suggests that endoscopic clipping may not be necessary to Isidro Machado, Tadahiko Masaki, Weiqi Sheng, Shinji Tanaka, prevent post-polypectomy bleeding after resection of large serrated polyps. Kazutomo Togashi, Paul Fockens, L. M. G. Moons, Evelien Dekker Introduction: Accurate risk estimation for lymph node metastasis (LNM) in T1 colorectal cancer (CRC) is critical to optimize further treatment. Currently, deep submucosal invasion (DSI) is considered a strong indicator for radical surgery. However, www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB81 Abstracts

FRIDAY, MAY 21, 2021 Colon and Rectum 1 Lecture

ID: 3524710 CHARACTERISTICS OF LARGE COLON POLYPS MISSED ON INDEX COLONOSCOPY IN PATIENTS REFERRED FOR ENDOSCOPIC MUCOSAL RESECTION: AN OBSERVATIONAL STUDY Allen R. Yu*, Philip Kozan, M. Phillip Fejleh, Alireza Sedarat, V. Raman Muthusamy, Stephen Kim Background: Colonoscopy remains the gold standard for colorectal cancer screening, but missed lesions on screening colonoscopy represent an important contributor to the development of interval colorectal cancer. Prior studies have estimated the prevalence of missed adenomas 10 mm at 2-6%. Methods: This was a retrospective study of all first-time referrals for endoscopic mucosal resection (EMR) of large colon polyps to a tertiary academic medical center over two years. Reports of the index colonoscopy, colonoscopy for large colon polyp EMR, and pathology were reviewed for all patients. Patients were included if there was at least one additional polyp, besides the lesion being referred, that was greater than 10mm in size identified on the colonoscopy referred for large colon polyp EMR. Information on the size, location, characteristics, and histology of these additional large polyps were obtained. A polyp was counted as missed on index colonoscopy if it was found on the colonoscopy referred for EMR but not documented on the index colonoscopy report. Results: Among a total of 389 patients referred for EMR of a large colon polyp, 41 (10.5%) patients had at least one additional large colon polyp. Of these 41 patients, 62 additional large colon polyps were identified. 14 of the 62 (22.6%) additional large polyps were missed on index colonoscopy. The average size of the 14 missed large polyps was 16.8mm (standard deviation 5.99mm). All missed polyps appeared sessile on endoscopy. A majority of the missed polyps (10 of 14, 71.4%) were located in the right colon. Despite their sessile appearance, most of the missed polyps (12 of 14, 85.7%) were classified histologically as tubular or tubulovillous adenomas and not as sessile serrated adenomas. None of the missed polyps were classified as adenocarcinoma on final pathology. Conclusions: In patients being referred for large colon polyp EMR, additional large colon polyps may be overlooked at time of index colonoscopy. Most of these missed polyps are sessile and located in the right colon. Interventional endoscopists should be cognizant of the possibility of finding additional large colon polyps in these high-risk patients.

FRIDAY, MAY 21, 2021 Colon and Rectum 1 Lecture

ID: 3520136 RISK OF METASTATIC RECURRENCE AFTER ADDITIONAL SURGERY IN RELATION TO THE VERTICAL TUMOR MARGIN OF ENDOSCOPIC RESECTION FOR T1B COLORECTAL CARCINOMA Tomoyuki Nishimura*, Shiro Oka, Yuki Kamigaichi, Hirosato Tamari, Yasutsugu Shimohara, Yuki Okamoto, Katsuaki Inagaki, Kenta Matsumoto, Hidenori Tanaka, Ken Yamashita, Yuki Ninomiya, Yasuhiko Kitadai, Shinji Tanaka Background and purpose: We previously reported that preceding endoscopic resection (ER) for T1 colorectal carcinoma (CRC) requiring additional surgery had no effect on patient’s prognosis (J Gastroenterol 2019). In addition, the Japanese Society for Cancer of the Colon and Rectum stated that the vertical tumor margin distance (the distance from the deepest invasion portion of carcinoma to the marginal termination resected by ER) of 500 mm or more is desirable for ER to reduce lymph node (LN) metastases. We analyzed the influence of vertical margin distance of ER for T1b (submucosal invasion > 1000mm) CRC on the metastatic recurrence and prognosis of patients who underwent additional surgery after ER.Method: A total of 215 consecutive patients with T1b CRC who underwent additional surgery after ER at Hiroshima University Hospital between February 1992 and June 2019 were enrolled. There were 105 patients who underwent resection by endoscopic submucosal dissection and 110 patients by endoscopic mucosal resection. We assessed 191 patients without LN metastases after additional surgery (average follow-up period, 73 months). Vertical margin distance of resected specimens by ER was classified into three groups: 104 patients with vertical margin distance of 500 mm or more (Group A), 43 patients with vertical margin distance of less than 500 mm (Group B), and 44 patients with vertical tumor margin positive (Group C). We analyzed the clinicopathological characteristics and prognosis of T1b patients among the three groups. Results: There were no significant differences in age, sex, tumor size, localization, gross type, main histology, lymphatic invasion, venous invasion, and budding grade among the three groups. Metastatic recurrence for each group was as follows: Group A (0%), Group B (11.6%; 2 lungs, 1 liver/lung

AB82 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts and 2 pelvic LNs; average period to recurrence is 26 months), and Group C (9.1%; 1 polyps between each academic year. Statistical analysis was performed with Welch’s liver/lung, 1 liver and 2 lungs; average period to recurrence is 31 months). The 5-year t-test and Chi-square test. Results: A total of 389 patients were referred for EMR of overall survival rate was 98.7% in Group A, 93.8% in Group B, and 95.5% in Group C; large and complex colon polyps that were not removed at index colonoscopy there was no significant difference among the groups. The recurrence-free 5-year including 122 patients in 2014-2015 and 267 patients in 2018-2019. Among the two survival rate was 100% in Group A, 84.5% in Group B, and 81.8% in Group C. Group groups, a total of 129 polyps and 337 polyps were identified and removed, respec- A had a significantly higher rate than Group B (pZ0.0006) and Group C tively. There were no significant differences in the age, gender and race among (pZ0.0003). The disease-specific 5-year survival rate was 100% in Group A, 97.4% in patients referred in the two time periods. There was no statistically significant dif- Group B, and 95.5% in Group C; group A had a significantly higher rate than Group ference in the size of the colon polyps identified on EMR. However, there was a C(pZ0.0313). Conclusions: Complete en bloc resection with sufficient submucosal trend towards significance in the number of polyps referred that were <15 mm in layer (vertical section distance >500 mm) by ER is necessary in patients with T1b CRC size when comparing 2018-2019 vs. 2014-2015 (n Z 98 vs. 36, p Z 0.065). There was to reduce the risk of metastatic recurrence after additional surgery. no difference in the anatomic location of the referred colon polyps. There was a trend towards significance in the type of pathology of the colon polyp with an increase in sessile serrated adenoma/polyps in 2018-2019 vs. 2014-2015 (n Z 85 (25.2%) vs 19 (14.7%), p Z 0.064). A significant increase in patients referred for FRIDAY, MAY 21, 2021jSATURDAY, MAY 22, 2021 large colon polyp EMR had at least 2 or more polyps found on subsequent colonoscopy when comparing 2018-2019 vs. 2014-2015 (n Z 48 vs. 6, p < 0.001). Colon and Rectum 1 Discussion: In patients referred for colorectal polyp EMR, there is a growing trend LecturejLecture that patients are more likely to have additional colon polyps at the time of repeat colonoscopy. While the overall colon polyp size has not changed, there may be an increasing number of smaller polyps and sessile serrated adenoma/polyps that are ID: 3523387 being referred for EMR. Given this trend, interventional endoscopists may consider EFFICACY OF REAL-TIME COMPUTER AIDED booking adequate time to account for the possibility of finding additional advanced DETECTION OF COLORECTAL NEOPLASIA IN A NON- adenomas. EXPERT SETTING: A RANDOMIZED CONTROLLED TRIAL Alessandro Repici, Marco Spadaccini*, Giulio Antonelli, Roberta Maselli, Piera Alessia Galtieri, Gaia Pellegatta, Antonio Capogreco, Sebastian Manuel Milluzzo, Gianluca Lollo, Elisa Chiara Ferrara, Alessandro Fugazza, Silvia Carrara, Andrea A. Anderloni, Arnaldo Amato, Andrea De Gottardi, Cristiano Spada, Franco Radaelli, Cesare Hassan Background & aims: One-fourth of colorectal neoplasias are missed during screening colonoscopies; these can develop into colorectal cancer (CRC). Several deep learning based real-time computer-aided detection (CADe) systems proved their efficacy in improving the performance of expert endoscopists in neoplasia detection. We performed a multicenter, randomized trial to assess the efficacy of a CADe system in detection of colorectal neoplasias in a non-expert setting to challenge the CADe impact in a real-life scenario. Methods: We analyzed data of consecutive 40- to 80-years-old subjects undergoing screening colonoscopies for CRC, post-polypectomy surveillance, or workup due to positive results from a fecal immunochemical test or signs or symptoms of CRC, at 5 European centers from July through September 2020. Endoscopists with a previous experience of <1500 colonoscopies performed all the exams. Patients were randomly assigned (1:1) to groups who underwent high-definition colonoscopies with the CADe system or without (controls). As CADe, we used a convolutional neural network with convolutional and max pooling layers (GI-Genius, Medtronic) that was integrated in the endoscopy system (i.e. real-time output on the same endoscopy monitor). A minimum withdrawal time of 6 minutes was required. The primary outcome was adenoma detection rate (ADR, the percentage of patients with at least 1 histologically proven adenoma or carcinoma). Secondary outcomes were adenomas detected per colonoscopy, and withdrawal time. Results: The final analysis included 660 patients (age: 62.310.0 years old; gender M/F: 330/330). ADR was statistically significantly higher in the CADe-group (176/330, 53.3%) than in the control group (146/330, 44.2%; OR: 1.44; 95% CI:1.06 to 1.96), as well as APC (1.26; 95% CI:1.14-1.38 vs 1.04; 95% CI:0.93-1.15; incident rate ratios, IRR:1.21; 95% CI:1.05-1.40). No statistically significant difference in withdrawal time (CADe: 8.11.61 minutes vs control: 7.91.53; pZ0.06) was observed. Conclusions: In a multicenter, randomized trial, we found that including CADe in real-time colonoscopy significantly increases ADR and adenomas detected per colonoscopy in a non-expert setting.

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Poster

ID: 3524723 REFERRAL TRENDS IN ENDOSCOPIC MUCOSAL RESECTION OF COLON POLYPS: A COMPARISON OF TWO TIME PERIODS Philip Kozan*, Allen R. Yu, M. P. Fejleh, Alireza Sedarat, V. Raman Muthusamy, Stephen Kim Introduction: Endoscopic mucosal resection (EMR) has emerged as a cost-effective and safe technique for removing large colon polyps with a lower risk of complications as compared to surgery. With the rise of colon polyp referrals, it is important to understand the trend in types of polyps that are referred for EMR. Methods: A retrospective chart review was performed to identify patients who underwent an index colonoscopy and were referred for colon polyp EMR with interventional endoscopists at a single tertiary academic center over two separate academic years (2014-2015 vs. 2018-2019). Our primary outcome was to determine if there was a difference in colon polyp size referred for EMR between the two time periods. Secondary outcomes were differences in location, pathology and total additional www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB83 Abstracts

SATURDAY, MAY 22, 2021 forward-viewing colonoscopy was 21.18. The adenoma detection rate for combined forward and retroflexion colonoscopy was 32.01. Conclusion: We found that com- Colon and Rectum 1 bined forward and retroflexion withdrawal technique during colonoscopy increases Poster the polyp and adenoma detection rates in comparison to standard colonoscopy. Larger, multi-center trials are necessary to validate these data. ID: 3527156 EXPERIENCE OF ENDOSCOPIC SUBMUCOSAL DISSECTION FROM SINGLE TERTIARY CENTER FOR SATURDAY, MAY 22, 2021 COLORECTAL NEOPLASMS: CHARACTERISTICS, Colon and Rectum 1 OUTCOMES, AND RECURRENCE Sakolwan Suchartlikitwong*, Nael Haddad, Paul A. Muna Aguon, Poster Kelly Zucker, Brian M. Fung, Mahmoud Bayoumi, Anam Omer, Teodor C. Pitea ID: 3524071 Introduction: Endoscopic submucosal dissection (ESD) has been introduced as a SELF-EXPANDING METALLIC COLORECTAL STENT minimally invasive approach to remove large colorectal mucosal lesions, suspected PALCEMENT GUIDED BY ULTRA-FINE ENDOSCOPE: A for advanced histology. Moreover, this procedure has replaced a surgical resection SINGLE CENTER’S RETROSPECTIVE STUDY. for the treatment of early colorectal neoplasms in some experienced centers. There are still a few data on long-term outcomes, recurrence, and complications after ESD. Jun Li*, Yao-Peng Zhang Method: We performed a retrospective chart review of patients who underwent ESD Aim: Self-expanding metallic stent (SEMS) placement has been recommended for to remove colorectal mucosal lesions between January 2015 and November 2020 malignant colorectal obstruction. Due to the limitation of conventional colonoscope (which diameter was usually more than 1cm), the technical failure rate is 2% to 10%. from a university referral center in Phoenix, Arizona. The procedure was performed fi by a single advanced-endoscopist. Data collected from medical records were However, the ultra- ne endoscopy can easily see the obstructive lesions directly and analyzed by using Student’s t-test and chi-square. Statistical significance was defined reach the proximal colon through the narrow segment in most cases. The aim of this < study was to verify the effectiveness and safety of stent placement guided by ultra- as p-value 0.05. Result: There were 49 patients, 57% male and 43% female, who fi fi underwent ESD for colorectal mucosal lesions at our center from January 2015 to ne endoscope which diameter was 5.0 mm (Fuji lm EG-530N, Tokyo, Japan). November 2020. The mean age was 67.4 years. The mean lesion size was 31.9 mm. Methods: The data of patients with malignant colorectal obstruction treated by The median procedure time was 93 minutes. Locations of ESD were at right colon endoscopic colorectal SEMS implantation in the Peking University Third Hospital (6.1%), transverse (12.2%), and left colon (81.6%). There were 22.4% (11/49) of from June 2018 to November 2020 were retrospectively analyzed. According to the high-grade dysplasia adenomas and 26.5% (13/49) of adenocarcinoma. En- bloc technical details, patients were divided into conventional colonoscope group (colonoscope group) and ultra-fine endoscope group (ultra-fine group). Gender, age, resection was done in 41 cases (83.7%), whereas 8 cases (16.3%) had a complete fi lesion location, maximum diameter, angle between endoscope and lesion (0 , < 90 resection by using snare due to large size and dif cult locations. Out of 49 patients, 27 (55%) had follow-up endoscopy at our center. The mean follow-up time was 15.3 and 90 ) were compared respectively. The time of inserting guidewire ( from months. Local recurrence was found in 3 patients (11.1%). Among advanced his- reaching the obstruction site to the guidewire passing through the obstruction) and tology lesions (high-grade dysplasia and adenocarcinoma), 50% involved submu- the whole operation time (from reaching the obstruction site to releasing the stent) fi and complications were observed. Results: A total of 47 patients were included in the cosa. R0 resection, de ned as negative deep and lateral margin, was achieved in 85% fi of advanced lesions. Patients, who had adenocarcinoma with a positive deep margin, study, including 11 patients in the ultra- ne group (male 6 cases, female 5 cases) and 36 patients in the colonoscope group (male 25 cases, female 11 cases) . The average were referred to oncology for chemoradiation. All of them had no local recurrence at Z the time of follow-up endoscopies with the longest follow-up of 3 years. Post-ESD age of the two groups was 61.7 13.9 year-old vs. 69.9 15.0 year-old (P 0.112). There was no significant difference in the site and the diameter of the lesions. The complications were 12.2% for delayed bleeding and 2% for micro-perforation which fi were treated successfully with endoscopic interventions. Conclusion: Endoscopic angle between the endoscope and the obstruction was less in the ultra- ne group (10 in 0,1< 90 and 090) than in the colonoscope group (8 in 0,26< 90 and 2 submucosal dissection (ESD) of colorectal neoplasms has favorable outcomes and Z fi safety profile. Complete resection of early-stage colorectal cancer can be achieved 90 )(P 0.000). The time of inserting guidewire was signi cantly shorter in the ultra-fine group (2.83.1 min) than in the colonoscope group (12.07.9 min) with a high rate. When combined with adjuvant chemoradiation and vigilant colo- Z fi noscopy surveillance, patients can remain in remission for many years. (P 0.01). However, there was no signi cant difference between the whole operation time (17.713.3 min vs.24.111.0 min, PZ0.120). No complications needed emergent treatment such as bleeding and perforation occurred in both groups. There was one case of stent falling off in the colonoscope group. In the ultra-fine group, a penetrating ulcer was found on surgical specimen in one case two weeks SATURDAY, MAY 22, 2021 later, but the patient had no symptoms. Conclusion: Guidewire placement guided by Colon and Rectum 1 ultra-fine endoscope was more quickly with higher success rate. However, as the stent can not be passed through the ultra-fine endoscope, the ultra-fine endoscope Poster has to be withdraw before the SEMS was inserted. It is necessary to further optimize the procedure and shorten the overall operation time. The safety of SEMS place- ID: 3523296 ment under ultra-fine endoscopy is also very good. COMBINED FORWARD AND RETROFLEXION WITHDRAWAL DURING COLONOSCOPY USING A SECOND-GENERATION SHORT-TURN RADIUS COLONOSCOPE Carlos Robles-Medranda*, Roberto Oleas, Juan M. Alcívar-Vásquez, Carlos Cifuentes, Haydee Alvarado, Raquel S. Del Valle, Miguel Puga-Tejada, Ariana C. Lopez Acosta, Hannah P. Lukashok Introduction: Colonoscopy is the screening method to prevent colorectal cancer; however, polyps and adenomas are missed indivertibly. Factors such as the location of polyps on difficult areas (proximal side of the ileocecal valve, haustral folds, flexures, or rectal valves). We aimed to evaluate the impact of combined forward and retroflexion withdrawal using a second-generation short-turn radius colonoscope during colonoscopy. Methods: a non-randomized, single-center prospective trial. Patients were submitted first to a standard high-definition screening colonoscopy. Then, a second procedure on the same patient combining forward and retroflexion was performed by a different operator. Lesions detected on the second procedure were considered as originally missed during standard colonoscopy. We calculated the polyp detection rate and the adenoma detection rate of both standard and combined colonoscopy techniques. Statistical analysis was performed on R.4.0.3. fi Results: A total of 203 patients were included for analysis. The median age was 57 Table. Charicteristics of patients in ultra- ne group and colonoscope years, 66% were female. The reason for colonoscopy was diagnostic on 81.3%, group. screening on 15.8%, and 3.0 % for surveillance. Regarding the size of the lesions, 74.5% of lesions detected on forward-viewing were < 5 mm. Whereas, on retroflexion 65.3% sized < 5mm and 34.7% between 5-10 mm. The polyp detection rate for forward-viewing colonoscopy was 39.90. The polyp detection rate for combined forward and retroflexion colonoscopy was 54.18. The adenoma detection rate for

AB84 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Poster

ID: 3526168 DON’T GIVE UP ON THEM YET: OLDER AGE IS ASSOCIATED WITH ADVANCED NEOPLASIA AT SURVEILLANCE COLONOSCOPY Bryant Megna*, Aaron Boothby, Amy Gravely, Zhuo Geng, Aasma Shaukat Background: Colorectal cancer (CRC) incidence and mortality have improved over the past decades, largely due to increased rates of CRC screening and subsequent surveillance colonoscopy, with the aim of detecting advanced neoplasia (AN) and CRC. Whether older individuals (age 70+) benefit from surveillance colonoscopy taking into account size, number and location of AN at baseline colonoscopy is not known. Our study aims were to assess the risk factors for advanced neoplasia at surveillance colonoscopy by age cohorts given the current interest in decreasing surveillance. Methods: We collected information from a cohort of U.S. veterans at a single center (nZ932) that had undergone two colonoscopy exams at least 6 months apart between 2010 and 2019. Univariate analysis was performed on clinical, endoscopic, and provider predictors associated with developing interval AN. Variables demonstrating a threshold of p<0.2 were promoted to a multivariate logistic regression. Specific tests of significance included two sample t-test (quantitative/continuous) and Pearson’s Chi-square (categorical). A Kaplan-Meier curve was created to illustrate time-to- Figure 1. Kaplan-Meier curve depicting probability of advanced neoplasia event. Results: Demographic and baseline characteristics of patients found to have (AN) on surveillance colonoscopy, stratified by patients older and younger AN on follow up colonoscopy compared to those without are depicted in Table 1. than 70 years. On multivariable regression, older age was the strongest predictor of AN on follow up colonoscopy, with an approximate 3.2% increase in odds per year (OR [per unit time] 1.032, 95%CI: 1.0079-1.0571, p<0.001). Time to follow up colonoscopy was also associated with risk of AN (OR 1.2, 95% CI: 1.0955-1.3164 xx; p <0.0001) . Modifiable risk factors such as high body mass index (BMI) and smoking status did SATURDAY, MAY 22, 2021 not influence rate of AN at surveillance colonoscopy. Further, provider adenoma Colon and Rectum 1 detection rate, index adenoma size, total adenoma burden, and dysplastic histology Poster were not predictive of AN at surveillance colonoscopy. Time-to-event (development of AN) analysis stratified by age above or below 70 (Log-rank, p<0.0001) is presented in Figure 1. Conclusions: Older age and time to surveillance colonoscopy are the ID: 3521049 strongest risk factors for AN in follow up colonoscopy. Adenoma size, location, RISK FACTORS OF ADVANCED COLORECTAL POLYP fl number or lifestyle risk factors did not in uence risk of AN at follow up colonoscopy. WITH SMALL AND INTERMEDIATE SIZE IN Our work suggests continuing timely surveillance in older individuals. INDIVIDUALS YOUNGER THAN 50 YEARS OLD Chun-Wei Chen*, Wey-Ran Lin Introduction: Colonoscopy screening for colorectal neoplasm is recommended at the age of 50 years old. Limited data on the characteristics of colorectal neoplasm less than 50 years old is available. The aim of this study is to investigate the characteristics of colorectal neoplasm and identify the risk factor of advanced colon polyp in individuals less than 50 years old. Patients and methods: This study was performed in a teaching medical center of northern Taiwan. From Jan, 2015 to Jan, 2017, patients who performed polypectomy with polyp size between 6 to 20 milli- meters and younger than 50 years old were enrolled in this study. The demography of patients and the polyp characteristics including polyp pathological findings, size, location and morphology were collected. Descriptive statistics and frequency were calculated. Univariate and multivariate logistic regression analyses were performed for the risk factors of polyp with villous component and high grade dysplasia. Sta- tistical significance was defined as p value < 0.05. Results: A total of 264 patients with 323 polyps were included in this study. The male patients were 183 (69.3%). The demography of patients and polyps were listed in Table 1. In advanced colorectal adenoma, there were 171 (52.9%) polyps 10 mm, 58 (18%) polyps with villous component and 2 (0.6%) polyps with high grade dysplasia. In multivariate analysis, the polyp size with increasing 1 mm and pedunculated shape were associated with villous component and high grade dysplasia in patients younger than 50 years old (Table 2). For polyp sized 10mm, the pedunculated shape was the only risk factor (ORs: 7.62, 95% CI: 3.32-17.49, p <0.001). Conclusions: Increased polyp size and pedunculated polyp shape are the independent risk factors of advanced colorectal polyps in individuals younger than 50 years old.

Table 1. Demographic and baseilne patient characteristics.

www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB85 Abstracts

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Poster

ID: 3523886 LONG-TERM OUTCOMES AND SURVIVAL AFTER ENDOSCOPIC OR SURGICAL RESECTION FOR T1 COLORECTAL CANCER: A MULTICENTER RETROSPECTIVE STUDY Hirohito Tanaka*, Shiko Kuribayashi, Masanori Sekiguchi, Atsuo Iwamoto, Yoko Hachisu, Yasumori Fukai, Tetsuo Nakayama, Kensuke Furuya, Tomoyuki Masuda, Kazuhiro Takahashi, Kyoko Marubashi, Toshio Uraoka Introduction: According to the American Gastroenterological Association (AGA) guidelines, the curative criteria of endoscopic resection (ER) for T1 colorectal cancer (CRC) are well/moderately differentiated adenocarcinoma or papillary carcinoma, no lympho-vascular invasion, submucosal invasion depth <1000mm, and budding grade (BD) 1. Although an additional surgery is recommended for non- curative ER, the incidence of lymph node metastasis (LNM) is less than 12%. Some patients do not undergo surgery due to their old age and perspective in clinical practice, their clinical outcomes are not fully evaluated. Aims ＆ methods: The aim of this study was to clarify clinical outcomes in patients with T1 CRC. A total of 471 consecutive patients were enrolled from April 2009 to August 2019 at 10 institutions. Exclusion criteria included evidence of familial adenomatous polyposis, hereditary nonpolyposis colorectal cancer, or inflammatory bowel disease; presence of active, malignant diseases in any other organs; presence of synchronous or metachronous advanced CRC. Risk factors of LNM and recurrence, and survival were analyzed. Results: The mean age of patients was 68.510.6 years. The location of the lesion was 320(67.9%) and 151(32.1%) in the colon and rectum, respectively. A number of patients with ER without additional SR (ER alone) were 149(curative resection 74, non-curative resection 75), those with SR (SR alone) were 242, and those with ER and additional SR (ER + additional SR) were 80. (i) Risk factor of LNM: LNM was found in 10(12.5%) patients with ER + additional SR and in 34(14.2%) patients with SR alone. In multivariate analysis, positive lymphatic invasion was the only significant independent risk factor for LNM (OR 8.8, 95% CI [2.78-28.2], p<0.01). (ii) Recur- rence: During the mean observation period of 1188927 days, recurrence was found in 14(3.0%) patients. No recurrence was found in the ER curative resection group. Although 48% (75/155) patients with ER non-curative resection did not receive additional SR, there was no significant difference in recurrence rate between ER alone with non-curative resection and ER + additional SR groups (5.3% (4/75) vs. 2.5% (2/80), respectively; pZ0.43). In the SR alone group, recurrence was found in 3.3% (8/242). The significant independent risk factor for recurrence was BD 2/3 (OR 6.1, 95% CI [1.17-31.8], p<0.01). (iii) Survival: There were 17 deaths during the observation period, but CRC-related death was found in only 2 cases (0.42%); one was ER alone with non-curative resection and the other was SR alone. Conclusion: This study suggests that the possibility of expanding the indication for ER of T1 CRC, because positive lymphatic invasion was the only risk factor for LNM and better long- term outcomes were shown despite including significant number of patients with ER alone with non-curative resection.

Table 1. Baseline clinical characteristics of the enrolled patients SATURDAY, MAY 22, 2021 Colon and Rectum 1 Poster

ID: 3524880 COMPARISON OF RISK OF METACHRONOUS LESIONS BY PRESENCE OF A SESSILE SERRATED LESION AMONG INDIVIDUALS WITH ADENOMA ON INDEX COLONOSCOPY Seung Wook Hong*, Ha Won Hwang, Dae Sung Kim, Jiyoung Yoon, Jin Wook Lee, Sang Hyoung Park, Byong Duk Ye, Jeong-Sik Byeon, Seung-Jae Myung, Suk-Kyun Yang, Jeongseok Kim, Dong-Hoon Yang Background & Aim: Surveillance guidelines suggest the interval of colonoscopy by stratifying the risk based on findings in index colonoscopy. However, the risk of metachronous lesions on the coexistence of adenoma and sessile serrated lesion (SSL) was rarely addressed. We aimed to evaluate the impact of the presence of Table 2. Logistic regression analysis for villous component and high synchronous SSL on the risk of metachronous lesions within a similar adenoma risk grade dysplasia group. Methods: We retrieved individuals with at least one more adenoma on index colonoscopy and they were stratified into four groups depending on the presence of SSL and low-risk/high-risk adenoma (LRA/HRA) on index colonoscopy. Subjects who undertook a surveillance colonoscopy at least 12 months apart were included in the analysis. We compared the risk of metachronous lesions including HRA, advanced adenoma (AA), or SSL within a similar adenoma risk group by the presence of SSL. Results: A total of 4,493 individuals were eligible for the analysis. The risk of metachronous HRA/AA had not increased significantly in the adenoma plus SSL group compared with isolated adenoma group, irrespective of LRA (HRA, 6/86 vs 231/3,297,

AB86 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts pZ1.00; AA, 0/86 vs 52/3,297, pZ0.64) or HRA (HRA, 11/64 vs 240/1,046, pZ0.36; an insignificant trend towards reduced PPB with post-polypectomy clipping in AA, 3/64 vs 51/1,046, pZ1.00). However, the risk of metachronous SSL in individuals Western populations compared to Eastern populations. Overall, we did not find that with synchronous SSL had significantly increased compared with those without SSL prophylactic clip placement reduced the risk for PPB. both in LRA (15/86 vs 161/3,297, p<0.001) and HRA (11/64 vs 61/1,046, pZ0.002). Conclusions: The presence of synchronous SSL does not increase the risk of metachronous HRA/AA compared with isolated adenoma but increased the risk of metachronous SSL.

Figure 1. Eligible individuals ﬂow diagram.

SATURDAY, MAY 22, 2021 Table 1. Comparison of risk of the metachronous lesion by the presence Colon and Rectum 1 of a sessile serrated lesion on index colonoscopy Poster

ID: 3523446 SATURDAY, MAY 22, 2021 TECHNICAL OUTCOMES AND RISK OF STRICTURE Colon and Rectum 1 AFTER ENDOSCOPIC SUBMUCOSAL DISSECTION FOR Poster LARGE COLORECTAL LESIONS Maselli Roberta, Marco Spadaccini*, Piera Alessia Galtieri, Gaia Pellegatta, Elisa Chiara Ferrara, Alessandro Fugazza, Silvia Carrara, ID: 3523875 Andrea A. Anderloni, Alessandro Repici POST-POLYPECTOMY BLEEDING WITH PROPHYLACTIC Background & aims: Endoscopic submucosal dissection (ESD) is a well-established CLIPS: EAST MEETS WEST approach for the minimally invasive treatment of colorectal (CR) neoplasia with Benjamin D. Renelus, Devika Dixit*, Daniel S. Jamorabo favorable outcomes in term of efficacy and safety. Although technical improvements Background: The rate of post-polypectomy bleeding (PPB) per colonoscopy is enable en-bloc removal of large circumferential and near-circumferential rectal fi 0.44%. Studies have shown that PPB rate is affected by polyp size and colon loca- lesions, the ef cacy outcomes, as well as the incidence of strictures and other ’ tion, but there has been no comparison between population regions. We sought to adverse events after rectal ESD, have only been described in few Eastern countries fi investigate the PPB difference when prophylactic clips were employed post-poly- experiences. The aim of this study is to assess ef cacy and safety outcomes of a pectomy between East- and West-based populations. Methods: We performed a cohort of patients treated with ESD for large rectal lesions in a tertiary Western systematic search of PubMed/Medline and Scopus databases for randomized center, with a particular focus on the risk of stricture. Methods: Between February controlled trials investigating the difference in PPB when polypectomy was under- 2011 and June 2019, a retrospective analysis of a prospectively maintained database taken with and without prophylactic clipping. Our primary endpoint was PPB dif- was conducted on patients treated by ESD for large rectal lesions that required ference with prophylactic clips between Western hemisphere (West) and Eastern 75% circumferential resection at Humanitas Research Hospital in Milan, Italy. The hemisphere (East) populations. Our secondary endpoint was overall PPB difference primary outcome considered for this study was the risk of stricture. Secondary between use of post-polypectomy clipping versus no clipping. To evaluate the pri- outcomes were en-bloc, and R0 resection rates, procedural time, and other adverse mary endpoint, we generated a bubble plot meta-regression (Figure 1). We also events. The curative resection rate was assessed for submucosal invasive lesions. performed a meta-analysis with fixed and random effects models to establish pooled Results: Over the study period, 213 consecutive patients underwent a rectal ESD. relative risk estimates using Mantel-Haenszel and Dersimonian-Laird methods, Eighty-eight of them (mean age: 68.5 12.9 years old; 50 -56.8%- males) required respectively. Forest plot with relatively risk (RR) and 95% confidence intervals (CI) 75% circumferential resection (32 circumferential resection) and were included in were likewise developed (Figure 2). Results: Two West-based studies and five East- the study analysis. The 94.3% of lesions were resected in an en-bloc fashion in a based studies including 4,687 polyps were included for analysis. When compared to mean procedural time of 110.6 63.2 min. The rate of R0 resection was 80.7%. Eastern populations, there was a trend toward significant reduction in PPB with use Eighteen out of 88 lesions (20.5%) resulted in CR neoplasia with submucosal inva- of prophylactic clips for Western populations (RR 0.53; 95% CI 0.28-1.02; pZ0.058). sion. Eight of them (44.4%) showed high-risk features of nodal involvement (non- There was no overall difference in PPB based on whether or not post-polypectomy curative resection) and were referred for surgery. A total of 3 (3.4%) peri-procedural clipping was undertaken (RR 0.83; 95% CI 0.59-1.16; pZ0.40). Conclusion: There is AEs (2 intraprocedural bleedings, 1 post-procedural perforation) occurred. Post-ESD www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB87 Abstracts rectal strictures occurred in 4 out of 80 patients (5.0%), being strictly associated to circumferential resections (4/32, 12.6%). The 4 patients underwent endoscopic balloon dilation with symptoms resolution. Conclusion: Rectal ESD is a safe and effective option for managing large rectal neoplasia in a Western setting. The risk of post-procedural stricture is associated to circumferential resections, and patients should be aware of the possible need of endoscopic dilations.

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Poster

ID: 3522208 THE FEASIBILITY OF COLORECTAL ENDOSCOPIC SUBMUCOSAL DISSECTION ON LESIONS WITH SCAR TISSUE: A RETROSPECTIVE STUDY IN A SINGLE TERTIARY CARE MEDICAL CENTER IN THE UNITED STATES Niranjani Venkateswaran*, Justin Roy, Ji-Min Park, Matthew T. Moyer, Mathew Abraham Figure 1. Pre and Post ESD intervention of both scarred and non-scarred Introduction: Endoscopic submucosal dissection (ESD) is a minimally invasive technique that enables en bloc resection of early gastrointestinal tumors and precan- colorectal lesion. cerous lesions, however, it is not widely used in the colon due to the thinner colonic wall, higher complication rates, and efficacy and safety of standard endoscopic mucosal resection (EMR). Limited data on colorectal ESD has been published in the United States. The purpose of this study is to determine the safety and efficacy of SATURDAY, MAY 22, 2021 using colorectal ESD in both scar-embedded and non-scarred colorectal lesions in a Colon and Rectum 1 single US tertiary care center. Methods: A retrospective chart review between January 2013 and April 2020 identified 159 patients who had undergone colorectal Poster ESD for en bloc resection due to the appearance of advanced pathology such as NICE 3, nongranular section, or Paris IIc; scarred lesions not amenable to standard ID: 3518085 EMR or a failed EMR attempt. The primary outcome was en bloc resection rates PREDICTING COLORECTAL ADENOMA AND ITS RISK between scarred and non-scarred colorectal lesions among lesions that were not amenable to EMR. Our secondary outcomes were tumor recurrences at 6-month FACTORS IN AFRICAN AMERICAN DOMINANT PATIENT follow-up and serious adverse events within 30 days. Results: Out of 159 colorectal POPULATION ESD procedures, the mean lesion size was 25.86 16 (15.86 - 41.86) mm, with an Hamid-Reza Moein*, Salina Faidhalla, Hersimren Minhas, Mahvish Khalid, average procedure time of 97 67 (30-164) minutes. Overall, the en bloc resection Paul H. Naylor, Bashar Mohamad “ rate was 52.2% (83/159) and the R0 resection rate among the non-scarred and en Introduction: Colorectal adenomas are precursors of colorectal cancer (CRC). There- ” bloc lesions was 41.3% but total of 49% (78/159) were unknown. Among the lesions fore, an optimal CRC prediction model should have the ability to predict adenomas. “ ” that were not amenable to EMR , en bloc resection was achieved in 64% (29/45) of We aimed to identify risk factors for colorectal adenomas in African American Z the scarred lesions, and 60.5% (46/76) of the non-scarred lesions (p 0.66). Lesions dominant patient population. In addition, we tested whether previously validated that were malignant or had high grade dysplasia were 36.4% (58/159). Follow-up clinical scores for CRC or adenoma detection can correctly predict the risk of colonoscopy was performed at a mean of 5.03 5 months, which was completed in identifying adenomas prior to colonoscopy. Methods: A retrospective, case-control, 73.5% (117/159) of the cases. About 3.41% (4/117) had tumor recurrences in which 3 chart review study. From a total of 1095 patients who had colonoscopy in the last 6 of them proceeded with surgery. In total, there were 6 perforations (3.7%), with 1 months of 2017, 52 patients with advanced adenoma (1cm, or high grade tubulo- requiring emergent surgery but no mortalities. Major bleeding event was 1/159 villous or villous, or high-grade dysplasia) were identified. Two age- and gender- (0.63%). Conclusion: Our study showed an overall lower en bloc and R0 resection matched controls were used as comparators. Patients with low-risk adenoma (i.e., rates compared to eastern countries. Our limitation with low R0 resections could be <1cm, and no high-risk histologic features) and no adenoma were served as positive possibly due to the inadequate margin surrounding the tumor. Although previous and negative controls, respectively. BMI, past medical history, family history, social fi literature including meta-analysis suggest brosis as one of the limiting factors in en history, use of aspirin and NSAIDs in past 30 days, and hormone therapy were re- fi bloc resections, we found no statistically signi cant difference between scarred and corded as potential risk factors of CRC. QCancer (http://qcancer.org/15yr/colorectal) non-scarred lesions. Despite this, colorectal ESD demonstrated a reasonable success was used to calculate the risk of CRC. Advanced adenoma detection risk is calculated < rate with a recurrence rate of 5% and was found to be relatively safe given a based on a validated formula from university of Minnesota (Gastroentrol Hepatol perforation rate of 3.7%, and no fatalities. While this is promising, further multi- IntJ 2017,2(1):00017). Results: 156 age- and gender-matched patients were analyzed center studies with a larger sample size are needed to better characterize the (52 patients in each group). Total of 89.7% African American and 10.3% Caucasian viability of colorectal ESD in the United States. were included. There was no significant difference in age and gender among 3 groups. Interestingly, among the evaluated risk factors, only chronic obstructive pulmonary disease (COPD) was more prevalent among advanced adenoma patients as compared to no adenoma (18.18% vs. 1.96%; pZ0.01). Mean 5-year CRC calculated risk was 0.550.06%, 0.400.03%, and 0.500.05% in advanced adenoma, low- risk adenoma, and no adenoma groups, respectively (pZ0.11). Similarly, there was no significant difference in the mean15-year CRC risk among 3 groups (2.380.26%, 1.780.13%, and 2.200.22%, respectively; pZ0.12). Raw probability scores for prediction of advanced adenoma was not significantly different among 3 groups (0.550.06%, 0.400.03%, and 0.500.05%, respectively; pZ0.45). Conclusion: COPD, irrespective of smoking history, is an important predictor of high-risk adenoma and may be incorporated in CRC risk calculation in African American dominant patient population. Using previously validated CRC risk calculators (QCancer) and advanced adenoma prediction probability models in patients where age and gender were removed as factors, we were not able to correctly predict patients with advanced adenoma from control patients. Our study demonstrates the diversity and different weight of risk factors in African American dominant patient population in comparison with other patient populations.

AB88 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

SATURDAY, MAY 22, 2021 Background and Aim: Polyps located at certain locations are difficult to resect and are usually referred to surgery due to concern for incomplete resection or adverse Colon and Rectum 1 events. However, surgery is associated with significant risks. Our study aimed to Poster assess the efficacy and safety of endoscopic resection of colorectal polyps in challenging locations. Methods: A retrospective single-centre review of the elec- ID: 3521113 tronic medical records of all patients who underwent polyp resection by two experienced endoscopists from 01/2011 to 12/2019 was undertaken. Patients who HIGH CONFIDENCE OPTICAL DIAGNOSIS OF SMALL underwent surveillance colonoscopies elsewhere or in whom follow-up duration was POLYPS AT COLONOSCOPY VERSUS <3 months were excluded. Data was abstracted for patient demographics, lesion HISTOPATHOLOGY: MOVING TOWARDS A NEW GOLD location and morphology, resection techniques, adverse events, recurrent/residual STANDARD? lesions, and need for surgery. Results: A total of 244 patients (mean age 67 years; 169 male) with 290 polyps in difficult locations were identified. The mean polyp size was Ahmir Ahmad*, Ana Wilson, Morgan Moorghen, Angad S. Dhillon, 20.8 mm (range: 2-90 mm) and 54% of the polyps were 20 mm in size. The lesions Siwan Thomas-Gibson, Noriko Suzuki, Adam Humphries, Adam Haycock, were described as sessile (56%) and flat (35%) in most cases. The more common Kevin J. Monahan, Margaret Vance, Brian P. Saunders difficult polyp locations were the hepatic flexure (46%), ileocecal valve (24%) and Introduction: Histopathology is regarded as the gold standard for diagnosis of small appendiceal region (13%). The majority of the lesions (271/290; 93.1%) were colonic polyps. However, there is growing interest in optical diagnosis and imple- removed by snare with/without submucosal fluid lift. Adjuvant therapy to snare mentation of a ‘resect and discard’ strategy. Our aim is to evaluate accuracy of his- resection was used in 37.9% of the lesions, including argon plasma coagulation, cold topathology reporting where a high confidence diminutive polyp optical diagnosis biopsy avulsion, endoloop and hot biopsy avulsion. Prophylactic clip closure was was made and to assess the impact of performing additional tissue section re-cuts, performed in 155/290 (53%) of the resection defects (average 5 clips/defect) and where there is a discrepancy. Methods: Eight bowel cancer screening colonoscopists endoscopic suturing was performed in 5/290 (1.7%) of the defects. Immediate in- optically diagnosed 639 diminutive polyps during the period Feb-Nov 2020 in the traprocedural bleeding and perforation occurred in 2 patients (managed by clip early phase of a prospective feasibility study of optical diagnosis (DISCARD3). Each placement) and 2 patients (managed by clip placement), respectively. Adverse polyp diagnosis was evaluated by the colonoscopist as high or low confidence. All events occurred in 25 patients (10.2%) within 30 days of polyp removal (15 delayed retrieved polyps were sent for histopathology. Discrepancy between high confi- bleeding, 4 perforation and 6 transmural burn syndrome); 8/25 patients required dence optical diagnoses and histopathology were re-reported by a second pathol- hospitalization. Residual/recurrent adenoma/polyp was present in 25/290 (8.6%) ogist blinded to the original optical and histological call. If discrepancy remained post resection sites: 6 cases underwent surgery and the remaining 19 were managed after re-review, the polyp was re-cut into deeper levels and a third blinded histo- endoscopically. Conclusion: In experienced hands, colorectal polyps in difficult lo- pathology review performed (see Figure 1). Results: Of 639 diminutive polyps, 468 cations can be managed effectively and safely with endoscopic resection. (73.2%) were high confidence optical calls and 171 (26.8%) were low confidence. High confidence optical diagnosis agreed with histopathology in 78.2% (366/468) of cases and disagreed in 21.8% (102/468). In cases of disagreement, the initial histopathology was reviewed and 7.8% (8/102) were due to histopathology error of which SATURDAY, MAY 22, 2021 3.9% (4/102) corrected on second review and 3.9% (4/102) corrected with deeper levels. There were no polyp cancers and 1 case of high-grade dysplasia. Conclusions: Colon and Rectum 1 Although the majority of errors in optical diagnosis were related to incorrect high Poster confidence calls a significant number were due to histopathology error. Change in practice to routinely perform additional deeper levels (ie 6 levels instead of 3) for small polyps appears to reduce this error rate by w50%. Optical diagnosis errors ID: 3525882 may be reduced by increasing the threshold for assignment of high confidence. THERMAL ABLATION OF POST-EMR-DEFECTS REDUCES ADENOMA RECURRENCE AFTER ENDOSCOPIC MUCOSAL RESECTION OF COLONIC POLYPS: A SYSTEMATIC REVIEW AND METAANALYSIS Pujan Kandel*, Mohamed Abusalih, Deepesh Yadav, Murtaza Hussain, Santosh K. Dhungana, Thair Dawood, Massimo Raimondo, Ghassan Bachuwa, Michael B. Wallace Introduction: Polypectomy during colonoscopy reduces colon cancer by 50%. Endo- scopic mucosal resection (EMR) is a standard technique for removal of large (>20mm) colorectal polyps. Adenoma recurrence is one of the key limitations of EMR which occur in 15% to 30% in first surveillance colonoscopy. The main hy- pothesis behind adenoma recurrence is due to left over micro-adenomas at the margins of post EMR defects. In this systematic review and meta-analysis, we evaluate the efficacy of snare tip soft coagulation (STSC) at the margins of mucosal defects to reduce adenoma recurrence and bleeding complications. Methods: Electronic databases such as PubMed and the Cochrane library were used for systematic literature search. Studies with polyps only resected by EMR, and active treatment: with STSC, comparator: non STSC were included. Random effects model was used to calculate the summary of odds ratio (ORs) and 95% Confidence Inter- vals. The main outcome of the study was to compare the effect of STSC versus non- STSC with respect to adenoma recurrence at first surveillance colonoscopy after thermal ablation of post-EMR defects and post procedural bleeding. Results: Total three studies were included in systematic review and meta-analysis. Total number patients who completed first surveillance in STSC group was 308 and non-STSC group was 294. Majority of polyps were resected from proximal colon compared to distal colon in both groups. There were no significant differences between treatment and comparator group in terms of mean age and polyp size. Adenoma recurrence Figure 1. Overview of study was observed in 24 of 308 cases (8%) with STSC and 75 of 294 cases (25%) without STSC (OR, 0.25, 95% CI: 0.15-0.41, PZ0.001), Fig 1. Post procedural bleeding was observed in 67/343 (19%) with STSC and 78/341 (22%) without STSC (OR, 0.74, 95% CI: 0.43-1.29) Fig 2. There was no significant heterogenicity among the trials (I SATURDAY, MAY 22, 2021 squareZ 0%, pZ0.4) and (I squareZ 0%, pZ0.41%). Conclusion: Thermal ablation of post EMR defects significantly reduces adenoma recurrence at first surveillance Colon and Rectum 1 colonoscopy. Poster

ID: 3527109 ENDOSCOPIC MANAGEMENT OF COLORECTAL POLYPS IN CHALLENGING LOCATIONS Fnu Chesta*, Meher Oberoi, Prabh G. Singh, Anmol Singh, Ganeev Bhangoo, Kevin T. Behm, Louis M. Wong Kee Song, Navtej S. Buttar www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB89 Abstracts

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Poster

ID: 3519884 IMPLEMENTATION OF A "DAY OF SYMPTOMS SIGMOIDOSCOPY (DOSS)" PROGRAM RESULTS IN EARLIER STAGE DIAGNOSIS OF LEFT-SIDED COLON AND RECTAL CANCER Matthew Fasullo*, Sarmed Al Yassin, Hamzeh Saraireh, Simran Singh, Pritesh R. Mutha, Tilak Shah Introduction: Colonoscopy as the initial test for rectal bleeding could delay diagnosis of rectal and left sided colon cancer, since colonoscopy generally requires sedation and bowel preparation. In 2014, our tertiary veterans hospital instituted a protocol FIGURE 1. METHODOLOGY AND DEMOGRAPHICS wherein primary care, emergency room, and other providers were instructed to direct patients with rectal bleeding to the endoscopy unit for unsedated sigmoidoscopy on the same day that they reported symptoms. The aim of our study was to determine whether this day of symptoms sigmoidoscopy (DOSS) program decreased time to diagnosis of rectal and left-sided colon cancer, and resulted in an earlier stage at initial diagnosis. Methods: We identified patients diagnosed with left sided (i.e. – distal to the splenic flexure) colorectal cancer (CRC) between 2005 to 2019 from our institutional cancer registry. We excluded patients with only right sided colon cancer, and asymptomatic patients in whom cancer was detected on routine screening or surveillance examinations. We included as cases (“DOSS group”) left sided CRC diagnosed on sigmoidoscopy from 2014 to 2019. Controls were left sided CRC patients diagnosed between 2005 and 2013 with either sigmoidoscopy or colonoscopy (“Pre-DOSS group”). Controls were propensity score matched 2:1 based on age, gender, reason for endoscopic assessment, and ASA classification. The primary outcomes compared between cases and controls were (a) incidence of advanced (i.e. - stage 3 and 4) CRC at diagnosis (b) days between onset of symptoms and CRC diagnosis. Results: 90 patients were included (30 cases and 60 controls) (Figure 1a). As expected, due to propensity matching baseline demographics were similar between the two groups (Figure 1a). Advanced (stage 3 and 4) CRC was lower in the DOSS compared to pre-DOSS group (13% vs. 30%, p 0.07). Early stage diagnosis (stage 1) was significantly higher in the DOSS compared to pre- DOSS group (63% vs 33%, p < 0.01). Days between onset of symptoms to CRC diagnosis was significantly lower in the DOSS compared to pre-DOSS group (15 vs. 77 days, p <0.01) (Figure 2). 1-year and 3-year mortality were similar between the two groups. Discussion: A DOSS program resulted in a sooner left-sided CRC diagnosis after symptom onset, and earlier stage of left-sided CRC at diagnosis. Such a protocol should be considered in settings where barriers exist towards rapid access FIGURE 2. PRIMARY AND SECONDARY OUTCOMES to colonoscopy. Larger multi-center prospective studies are necessary to confirm that our results can generalize to other settings.

AB90 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

SATURDAY, MAY 22, 2021 study essentially conﬁrmed the data promised by Exact Science. Though it seems to be vulnerable to delay- which does appear to be more prominent in the COVID 19 Colon and Rectum 1 pandemic era- a positive Cologuard test can convince a reluctant patient to undergo Poster a life-saving colonoscopy.

ID: 3515704 HIGH PREVALENCE OF DYSPLASIA IN PROXIMAL SESSILE SERRATED LESIONS Yi Yuan Tan*, Sei Kiat Tay, Yu Jun Wong, James Weiquan Li, Boon Eu Kwek, Tiing Leong Ang, Lai Mun Wang, Malcolm Tan Background and Aim: Proximal colorectal cancers (CRCs) account for up to half of interval CRCs. Sessile serrated lesions (SSLs) are precursors to CRC. Proximal sessile serrated lesions (pSSLs) are associated with higher risks of dysplasia and progression to proximal CRC, the prevalence of dysplasia and characteristics predictive of dysplasia among proximal SSLs (pSSLs) are not well studied.We aimed to determine the prevalence and predictors of dysplasia among pSSLs. Methods: In this retrospective, observational study conducted in a tertiary referral hospital, we systematically reviewed all endoscopically resected colonic polyps at our centre between January 2016 and December 2017. Clinical and endoscopic data of patients with at least one pSSL were retrieved from electronic medical records. We compared the clinic-pathological features of pSSLs with and without histological evidence of dysplasia. Results: Among 637 patients were reviewed (mean age 63 years, 52.2% were male), we identified 90 pSSLs. The median size of pSSLs was 4mm (IQR: 3- 6mm), of which 13.3% were 10mm. pSSLs were most commonly detected in the ascending colon (51.1%) followed by cecum (26.7%) and transverse colon (22.2%). The prevalence of dysplasia among pSSLs was 50.0% (45/90). Among pSSLs with dysplasia, 60% had polyp size<5mm. Factors that were significantly associated with the presence of dysplasia among pSSLs were older age (65.9 vs 60.1 years, pZ0.034) and polyp size 10mm (83% vs 45%, pZ0.013). Synchronous SSLs, smoking history and family of CRC were not predictive of dysplasia among pSSLs. After adjusting for age, pSSLs 10mm is predictive of dysplasia among pSSLs [OR: 5.98 (95% CI: 1.21 – 29.6)]. Conclusions: Our study highlights a high prevalence of dysplasia among pSSLs, with polyp size 10mm being predictive of dysplasia among pSSLs. As dysplasia can still occur in a significant proportion of diminutive polyps (<5mm), en- bloc endoscopic resection for all pSSLs is crucial to facilitate accurate histopathological examination for dysplasia, the presence of which warrants shorter surveillance interval.

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Poster SATURDAY, MAY 22, 2021 Colon and Rectum 1 ID: 3527212 Poster A RETROSPECTIVE COHORT STUDY OF PATIENTS WITH POSITIVE COLOGUARD RESULTS AT A RURAL TERTIARY ID: 3524643 COMMUNITY HOSPITAL RISK FACTORS FOR HIGH-RISK COLORECTAL Jane E. Lindsay*, Stewart Hargrove, Chuan Long Miao Introduction: Since receiving FDA approval in 2014, the use of multitarget stool DNA ADENOMA AT THE FOLLOW-UP COLONOSOPY IN testing (MT-sDNA or Cologuard) testing has become a reputable option for colo- PATIENTS WITH REMOVED HIGH-RISK ADENOMA/ rectal cancer (CRC) screening amongst appropriate patient populations. The high EARLY COLORECTAL CANCER: A PROSPECTIVE sensitivity provided by Cologuard promises providers a powerful screening tool for COHORT STUDY colorectal cancer. The original study evaluating the statistical parameters of Colo- Eun Ji Lee, Hyuk Yoon, Min Kyu Kim, Cheol Min Shin, Young Soo Park, guard, should represent a general patient population. However, given the controlled Nayoung Kim, Dong Ho Lee* nature of clinical trials, further evaluation in real-life clinical practice was needed. Background/Aim: To evaluate the risk for high-risk colorectal adenoma/neoplasm Aim: To confirm the potential colonoscopy findings listed by Exact Science on (HRCAN; 3 or more adenomas, adenoma 1cm, adenoma with high-degree positive Cologuard test results in real-life clinical setting. Methods: In this study, data dysplasia and/or villous component, or in situ cancer), in patients who underwent of all patients referred to our gastroenterology clinic with a positive Cologuard test endoscopic resection for high-risk colorectal polyp (HRCP; 3 or more polyps, were retrospectively collected. Patients were selected from a 34 month time window adenoma or serrated lesion 1cm, adenoma with high-degree dysplasia and/or (1/1/2018-9/30/2020). Clinical parameters such as age, nicotine use and wait time villous component, or in situ cancer). Methods: Patients undergoing endoscopic (Table 1, 2) were collected. We defined wait-time as the period between the time a resection for HRCP were prospectively enrolled and they were recommended Cologuard test was ordered to the time a follow up colonoscopy was performed. follow-up colonoscopy one year later. The primary outcome was development of Results: In total 54 patients were referred to our clinic with a positive Cologuard test HRCAN in the first follow up colonoscopy. Multivariate logistic regression was per- result during the 34 month time period. Twelve patients were excluded owing to not formed to evaluate the risk factors for HRCAN. Results: In total, 378 adults with having completed a colonoscopy. One of the remaining 42 patients in fact had a HRCP removed by colonoscopy were enrolled in the cohort. 228 patients (60.3%) negative Cologuard result. Leaving a total of 41 patients for analysis. underwent follow up colonoscopy and the median follow up interval was 371.5 days. Within this cohort, two patients were found to have CRC, 13 were found to have an Among 228 patients, 35 had HRCAN at the first follow up colonoscopy; 28 had 3 or advanced 4adenoma, 15 had a non-advanced adenoma and 11 had negative findings more adenomas, 4 had adenoma 1cm, 6 had adenoma with villous components, (table 3, 4). Regarding prior screening history, only 17 patients total had previously and 1 submucosal cancer. We calculated the odd ratio (OR) for each variable and undergone screening. Of the remaining 24 previously unscreened patients, one was only hypertension (HTN) was a statistically significant; HRCAN occurred in 17 of 34 found to have a CRC and 11 were found to have advanced adenomas. patients (50%) in patients with HTN and 18 of 194 (9.3%) in patients without HTN, Though the wait-time was mostly under 5 months, delays were found up to 17 with an OR of 2.08 [95% confidence interval, 1.00 to 4.31]. The presence of HRCAN months. Both of the patients found to have CRC had extensive delays (Table 5). or HRSL at the first colonoscopy did not significantly affect the occurrence of Discussion: In addition to essentially matching the statistical data listed by Exact Sci- HRCAN at the first follow up colonoscopy. Besides 35 cases of HRCAN, we found 7 ence our study found several secondary observations. Cologuard is being utilized on high risk serrated lesions (HRSL; sessile serrated adenoma or hyperplastic 1cm, patients who have previously avoided screening colonoscopy. And unlike a any traditional serrated adenoma, 3 or more serrated polyp). Conclusion: HTN is a screening colonoscopy, the Cologuard is plagued with delays at multiple stages. risk factor for developing HRCAN at the 1-year follow-up colonoscopy. Furthermore, Conclusions: With the exception of detecting more non-advanced adenomas, our given that high-risk adenomas and serrated lesions were found in 18.4% of patients, www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB91 Abstracts

1-year follow-up colonoscopy is thought to be meaningful in patients with removed SATURDAY, MAY 22, 2021 high-risk adenoma/early colorectal cancer, especially those with hypertension. Colon and Rectum 1 Lecture

SATURDAY, MAY 22, 2021 ID: 3523373 Colon and Rectum 1 NON-CURATIVE ENDOSCOPIC SUBMUCOSAL Poster DISSECTION (ESD) FOR COLORECTAL CANCER: CLINICAL OUTCOMES AND PREDICTORS OF ID: 3522572 RECURRENCE COLD SNARE POLYPECTOMY VERSUS COLD FORCEPS Marco Spadaccini*, Michael J. Bourke, Roberta Maselli, Mathieu Pioche, POLYPECTOMY FOR DIMINUTIVE AND SMALL Pradeep Bhandari, Jeremie Jacques, Amyn Haji, Dennis Yang, Eduardo Albeniz, Michal F. Kaminski, Helmut Messmann, COLORECTAL POLYPS: A SYSTEMIC REVIEW AND META- Alberto Herreros De Tejada, Sandro Sferrazza, Boris Pekárek, ANALYSIS OF RANDOMIZED CONTROLLED STUDIES Jerome Rivory, Sophie Geyl, Shraddha Gulati, Peter V. Draganov, Justin Chuang*, Azizullah Beran, Sami Ghazaleh, Yasir Alabboodi, Neal C. Shahidi, Hossain Ejaz, Carola Fleischmann, Edoardo Vespa, Mohammed Mhanna, Omar Srour, Hazem Ayesh, Ali Nawras andrea iannone, Asma A. Alkandari, Cesare Hassan, Alessandro Repici Introduction: Diminutive (1-5mm) and small (6-9 mm) colorectal polyps are Background and Aim: Endoscopic submucosal dissection (ESD) is an organ-preser- frequently found during screening colonoscopy. Cold snare (CSP) and cold for- ving approach pursuing curative intent for the removal of superficially invasive ceps (CFP) are commonly used techniques for the removal of diminutive and small colorectal cancers (CRCs) with negligible risk for lymph-node metastasis. polyps. However, the optimal technique as regards effectiveness and safety remains Conversely, additional surgical resection is recommended in case of high risk of uncertain. Therefore, we conducted a systematic review and meta-analysis of all nodal involvement based on histo-pathological features. However, both the actual randomized controlled studies that compared the effectiveness and safety of CSP risk of a lymph-node disease and the clinical outcomes of patients who underwent versus CFP in diminutive and small colorectal polyps. Methods: We performed a non-curative ESD has never been investigated. The aim of this study is to report comprehensive literature search using the MEDLINE and EMBASE databases from outcomes of these patients from a large Western cohort. Methods: This was a inception through November 2020. Only randomized controlled studies (RCTs) that retrospective analysis of consecutive patients with CRC who underwent ESD at 13 compared CSP versus CFP were included. The primary outcome of interest was the tertiary-care centers. All lesions with histo-pathologic features of high risk of nodal incomplete resection rate (IRR). Secondary outcomes were procedure time, failure involvement were considered for the analysis, regardless of post-endoscopic man- of tissue retrieval, post-polypectomy bleeding, and perforation rates. All meta-ana- agement (Conservative vs Surgery). Primaryoutcomes were disease recurrence, lyses were conducted using a random-effect model. Pooled rates were reported as fi death and disease-related death rates after non-curative ESD in the two groups. As risk ratios (RR) or mean difference (MD) with 95% Con dence Interval (CI). Het- secondary outcomes, we assessed the rate of residual disease (RD) at both the erogeneity was assessed using the Higgins I2 index. Results: Eight RCTs, including a previous resection site and regional lymph-nodes among patients who underwent total of 958 patients with 1168 polyps (554 in CSP and 614 in CFP) met our inclusion fi fi surgery. Endoscopic and histologic variables were investigated as risk factors for RD. criteria and were included in the nal analysis. The IRR was signi cantly lower in CSP Results: From October 2012 to November 2019, 3373 patients have been treated by group compared to CFP group: 6% vs. 11.9%; RR -0.06, 95% CI [-0.10, -0.02], P Z Z fi colorectal ESD and 207 non-curative resections were considered for the analysis. 0.003, I2 35% (Figure 1). Failure of tissue retrieval rate was signi cantly higher in The 60.9%(nZ126) of these patients were referred for surgery, and the remaining CSP group compared to CFP (RR 9.60; 95% CI [2.20, 41.77], P Z 0.003, I2 Z 0%) Z fi 39.1%(n 81) were followed up. In a mean time of 27.6 18.6 months, there was no (Figure 2). Only two studies reported procedure time which was signi cantly shorter difference in term of recurrence rate between the two groups(pZ0.30). The Con- in CSP group compared to CFP group MD -5.87, 95% CI [-10.86, -0.88], P Z 0.02, I2 Z servative group showed a higher risk of death for any causes compared to the 47% (Figure 2). There were no adverse events found in both groups including Surgery group(HRZ3.99, pZ0.013). Conversely no difference was reported perforation, and post-polypectomy bleeding. Conclusions: Compared to CFP, CSP considering disease-specific survival rate. Among patients who underwent additional showed a lower incomplete resection rate and shorter procedure time. However, surgery, 25 patients(19.8%) had histological evidence of RD, with lymphatic-vascular CSP had a higher failure of tissue retrieval rate. Further studies with a larger sample Z Z > Z Z fi invasion (HR 3.48, p 0.009) and depth of invasion sm (HR 4.98, p 0.017) size are warranted to con rm our results. emerged as independent predictors. Conclusions: Additional surgical resection may be not clinically relevant in all cases of non-curative ESD. Lymphatic-vascular invasion and/or the neoplastic involvement of the muscular layer should strongly suggest a surgical approach.

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Lecture

ID: 3526954 FOUR-YEAR PROGNOSIS SURVEY AFTER COLORECTAL ESD -MULTICENTER PROSPECTIVE STUDY AMONG JAPANESE FOREFRONT- Keita Harada*, Nozomu Kobayashi, Ken Ohata, Yoji Takeuchi, Akiko Chino, Masayoshi Yamada, Yosuke Tsuji, Kinichi Hotta, Hiroaki Ikematsu, Toshio Uraoka, Takashi Murakami, Hisashi Doyama, Takashi Abe, Atsushi Katagiri, Shinichiro Hori, Tomoki Michida, Takuto Suzuki, Masakatsu Fukuzawa, Shinsuke Kiriyama, Kazutoshi Fukase, Yoshitaka Murakami, Hideki Ishikawa, Yutaka Saito Backgrounds and Aims: Colorectal endoscopic submucosal dissection (C-ESD) has been developed by Japanese expert colonoscopists, which is one of the most effective treatments for early-stage cancer due to its high en-bloc resection rate and high accuracy of histopathological evaluation. There were, however, few reports which systematically investigated the treatment results, especially long-term recurrence rates so far. The aims of this study were to clarify the prognostic outcomes of C-ESD though a large-scale multicenter prospective study. Materials and Methods: From February 2013 to January 2015, 1,883 patients were enrolled in this study from 20 institutions all over Japan and C-ESD was performed on a total of 1,965 lesions. Among them, 1,577 lesions of 1,493 patients who underwent follow up colonoscopy at least once within four years after C-ESD were analyzed. Results: The median age at treatment was 69 y-o (31-89). The average tumor size of the resected specimen was 34.516.4 mm. 1,214 of 1,305 lesions which were removed in complete en-bloc fashion by means of ESD were ﬁnally diagnosed as pathologically curative. Out of

AB92 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts remaining 363 lesions, 107 underwent additional surgery due to non-curative resection. 1,000 patients have underwent twice or more surveillance colonoscopies for over two years after C-ESD. Local recurrence has occurred only in five lesions in different patients (0.4% of 1,198 lesions without additional surgery). Among them, four were found early within 16 months at the site after R1 resections of intramucosal cancer. The other one recurred in the scar of T1a (submucosal slight invasion) cancer which has been considered as curative resection and was first found during a second surveillance performed in the third year after ESD. All five cases were re- treated endoscopically, and all resected specimen were adenomas, resulting in complete cure. Meanwhile, metachronous colorectal neoplasia was found in 33/ 1,493 (2.2%) patients within three years after C-ESD. Among those 33 lesions, 15 were invasive cancers and 13 required surgical operation as a retreatment. There was a statistically difference in the occurrence of metachronous colorectal neoplasia between patients who had harbored single C-ESD lesion and those who had been with multiple C-ESD lesions (1.7% vs. 8.3%, p Z 0.001), although there was no difference according to the curability of C-ESD lesion(s). Discussion: C-ESD had a high curative resection rate and the risk of local recurrence within at least four years was extremely low. On the other hand, the risk of occurrence of metachronous colorectal neoplasia within four years tended to be high, especially in patients who had underwent C-ESD for multiple lesions. Conclusions: Surveillance colonoscopy within four years after C-ESD should be paid attention to metachronous colorectal Table 1 neoplasia rather than local recurrences.

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Lecture

ID: 3526950 USE OF A DOUBLE BALLOON PLATFORM FACILITATES ENDOSCOPIC SUBMUCOSAL DISSECTION (ESD) OF COMPLEX COLON LESIONS AND DECREASES POST ESD LENGTH OF STAY(LOS): A SINGLE CENTER CASE MATCHED STUDY Stavros N. Stavropoulos*, Nasim Parsa, Jessica L. Widmer, Maaz B. Badshah, Tarek H. Alansari, Dmitriy O. Khodorskiy, Rani J. Modayil Background: ESD in the colon is challenging. A new double balloon (DB) platform (DiLumen, Lumendi, Westport, CT) is proposed to facilitate colon ESD by improved Table 2 endoscope stability. It may accelerate safer patient discharge by enabling routine suturing of the ESD defect. It allows rapid, easy insertion of the endoscopic suturing device (Overstitch, Apollo Endosurgery, Austin, TX) via the balloon-anchored sheath of the DB platform, which can otherwise be challenging to advance beyond the sigmoid, so typically less secure endoclips are used for closure. We aim to assess SATURDAY, MAY 22, 2021 potential benefits of DB-assisted ESD (DBA-ESD) compared to conventional ESD (C- Colon and Rectum 1 ESD) for complex colon lesions. Methods: From 1/18 to 3/20, 130 colon lesions had Lecture DBA-ESD. Initial 50 cases were excluded to mitigate DBA-ESD learning curve bias. Subsequent 80 were matched to 80 C-ESDs performed prior to the DBA-ESD period (2016-2017, after the operator’s first 300 ESDs, avoiding learning curve bias for C- ID: 3527049 ESD). Propensity score matching was used for age, gender, lesion area (cm2), ENDOSCOPIC MUCOSAL RESECTION (EMR) VERSUS difficult location, and prior lesion manipulation (tattoo, argon plasma, EMR)/fibrosis. ENDOSCOPIC SUBMUCOSAL DISSECTION (ESD) FOR Procedure time and dissection speed were compared to assess how DB facilitated ESD. Analysis comparing 45 DBA-ESDs with suturing of the defect vs 45 propensity- FLAT COLORECTAL POLYPS GREATER THAN OR EQUAL score matched C-ESDs with endo-clip closure was performed to determine if su- TO 20MM: COST CONSEQUENCE MODEL turing of the ESD defect minimizes admission rates. The lower number for this Stavros N. Stavropoulos*, John Hauschild, rituparna basu, analysis is because routine suturing of the ESD defect was only done later in our Jessica L. Widmer, Rani J. Modayil DBA-ESD experience, after developing a method to insert the gastroscope length Background: EMR has been shown to be less morbid and more cost-effective relative suturing device through the colonoscope-length DB sheath. Results: There was no to surgery for flat colon polyps greath than 2cm. Shortcomings include inability to difference between the 80 C-ESDs and 80 DBA-ESDs baseline characteristics (Table resect poorly lifting lesions and piecemeal resection which results in higher recur- 1). There were no severe AEs that required surgery, IR, other interventions, or rence rates and poor histologic margin assessment. ESD offers reliable en bloc, prolonged hospitalization. Median dissection speed was significantly faster and total margin negative resection (R0) with associated lower recurrence rates (and thus ESD time significantly shorter in the DBA-ESD group. [Table 1]. In the analysis of 45 presumably lower rates of surveillance colonoscopies and treatment of recurrences). matched C-ESD patients with endo-clip closure vs. 45 D BA-ESD patients with su- On the negative side, from a cost perspective, colon ESD may have higher compli- tured closure there were no significant differences in baseline characteristics. The cations and procedural costs and a long learning curve. In the absence of random- LOS was significantly shorter in the DBA-ESD group with a higher same day ized data, cost comparisons are dependent on modeling. Some prior attempts have discharge rate [Table 2]. Conclusion: We performed a case-control study of DBA- favored EMR but only focused on the initial procedure without factoring in the need ESD vs C-ESD for colon lesions using propensity score matching of cases and con- for surveillance colonoscopies. With the rising number of colon ESD centers of trols from a large prospective US single center cohort with a high volume of chal- excellence in the US, it would be topical to analyze the overall treatment episodes. lenging lesions including w50% with prior manipulation and difficult location. The The aim of our study was to compare the cost consequences of EMR vs. ESD for a DB platform, by offering endoscope stabilization and easy insertion of the endo- hypothetical cohort of patients with flat colon lesions >20mm. Methods: Cost scopic suturing device for secure ESD defect closure increased colon ESD speed, consequence model from a provider perspective using TreeAge Pro software. Actual reduced overall ESD time, decreased LOS and increased the same-day discharge cost information for procedures, intra-operative and post-operative complications, rate. Further studies are needed to confirm these promising results. was obtained from 2017 healthcare data sourced from the Premier Database, while the probability of an outcome was obtained from published literature. Since CPT codes do not exist for ESD, proxy procedure costs were assigned based on time parameters. Piecemeal EMRs were defined as EMR procedures 45 and <90 minutes, while ESD procedures were defined as resection procedures >90 minutes. Recurrences detected on colonoscopy plus biopsy (CBx) were followed by colonoscopy with salvage treatment(s), sensitiviy analysis with variant scenarios was also www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB93 Abstracts performed. Results: Costs and event probabilities appear in table I and decision tree SATURDAY, MAY 22, 2021 in fig. 1. Weighted costs: EMR $2,268, ESD $4,145, CBx $1,473, colectomy $13,492. After 100 Piecemeal EMR and ESD procedures were run through the initial pro- Colon and Rectum 1 cedure and surveillance model the overall cost per EMR patient was $7,840 Lecture compared with $7,040 for ESD. One hundred patients run through the ESD plus surveillance treatment arm results in 8 less surgeries, 21 less further endoscopic ID: 3520676 resections, and 79 less surveillance colonoscopies than EMR plus surveillance. An alternate scenario where EMR for a recurrence is performed at the same session as PREDICTIVE FACTORS FOR INTERRUPTION, the surveillance colonoscopy saves approximately 24 surveillance colonoscopies and PIECEMEAL RESECTION, AND PERFORATION AFTER results in a lower EMR cost of $7,480) reducing the per treatment episode cost STANDARDIZATION OF COLORECTAL ENDOSCOPIC savings of ESD to $440. Conclusion: ESD has the potential to reduce costs and more SUBMUCOSAL DISSECTION importantly patient burden by not only reducing the number of surgeries, but also the number of coloscopies for surveillance and salvage resections of recurrences. Yuki Kamigaichi*, Shiro Oka, Shinji Nagata, Masaki Kunihiro, Toshio Kuwai, Yuko Hiraga, Akira Furudoi, Seiji Onogawa, Hideharu Okanobu, Takeshi Mizumoto, Tomohiro Miwata, Shiro Okamoto, Hidenori Tanaka, Ken Yamashita, Yuki Ninomiya, Shinji Tanaka Background and Aim: Colorectal endoscopic submucosal dissection (ESD) has been standardized in Japan; however, interruption, piecemeal resection, and perforation are persistent problems. This study aimed to evaluate the predictive factors for above problems after standardization of colorectal ESD. Patients and Methods: This multi-center prospective observational study from the Hiroshima Gastrointestinal Endoscopy Research Group (11 institutions; Hiroshima University Hospital and 10 affiliated hospitals) included a total of 2,423 consecutive patients (1,453 men, mean age: 6910 years) who underwent ESD for 2,592 colorectal tumors between August 2013 and December 2018. We evaluated the predictive factors for interruption, piecemeal resection, and perforation in relation to clinicopathological and endoscopic features (tumor size, location, situation, growth type, pathological diagnosis, depth of invasion, bleeding during the procedure, degree of submucosal fibrosis, history of biopsy, history of local endoscopic treatment, history of abdominal surgeries, operator experience, the retrograde approach, time of the procedure, and scope operability). We also evaluated the predictive factors for severe submucosal fibrosis using preoperatively assessable variables without a history of local endoscopic treatment. Results: ESD was performed by a total of 49 endoscopists (9 ex- Table 1 perts and 40 non-experts). The mean size of tumors was 3014 mm, and the mean procedure time was 8468 min. En bloc resection rate was 96.4% (2,499/2,592), and the incidences of interruption, piecemeal resection, and perforation were 0.7% (18/ 2,592), 2.9% (75/2,592), and 3.0% (78/2,592; 73 perforations during procedure and 5 delayed perforations), respectively. Emergency surgery was required in 16.4% (12/ 78) of perforation cases. Multivariate analysis identified followings; 1) the predictive factors for interruption: occurrence of perforation during procedure, deep submucosal invasion (>1,000 mm), poor scope operability, and severe submucosal fibrosis, 2) the predictive factors for piecemeal resection: poor scope operability, severe submucosal fibrosis, and long procedure time (85 min), 3) the predictive factors for perforation during procedure: severe submucosal fibrosis, poor scope operability, long procedure time (85 min), and tumor size (40 mm). Severe submucosal fibrosis was identified as a common predictive factor for interruption, piecemeal resection, and perforation, and it was observed in 18.7% (230/1,228) of the lesions on the fold or flexure. Conclusion: Severe submucosal fibrosis and poor scope operability are the common predictive factor for interruption, piecemeal resection, and perforation after standardization of colorectal ESD. Prediction of severe submucosal fibrosis prior to ESD was difficult.

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Lecture

ID: 3521919 IMPACT OF GROSS TUMOR MORPHOLOGY ON THE CLINICAL OUTCOMES OF NON-METASTATIC COLON CANCER : MULTICENTER RETROSPECTIVE COHORT STUDY Decision Tree So Jung Han*, Bun Kim, Dae Bum Kim, Jae Hyun Kim, Il Hyun Baek, Jun Lee, Byung Ik Jang, Hyun Gun Kim, Hyun Seok Lee, Jae Jun Park Background/Aims: There has been no data regarding the association between gross morphology and clinical outcomes of colon cancers. We aimed to investigate the relationship between endoscopic features and outcomes of non-metastatic colon cancer. Methods: The study is a retrospective analysis based on the colon cancer cohort data of the colon cancer study group in the Korean Society of Gastrointestinal Cancer. Patients were followed-up and treated for colon cancer from 2010 through 2019. Data for clinical characteristics and treatment outcomes were retrieved. All patients received curative endoscopic or surgical resection as initial therapy. Colon cancer gross morphology was categorized into two groups, including ﬂat/ulceroin- ﬁltrative type or fungating/ulcerofungating type based on endoscopic images. Stag- ing of colon cancer followed AJCC 7th guideline. In multivariate Cox regression analysis, the following variables, including age, gender, family history of colon cancer, Carcinoembryonic antigen at diagnosis, diabetes mellitus, staging, tumor location and gross tumor morphology was included. Results: A total of 1205 patients

AB94 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

(mean age 6412 years, male 60.1%) were included. Regarding gross tumor SATURDAY, MAY 22, 2021 morphology, 343 (28.5%) patients showed flat/ulceroinfiltrative type; meanwhile 862 (71.5%) patients showed fungating/ulcerofungating type. Flat/ulceroinfiltrative type Colon and Rectum 1 cancer showed a significantly shorter time to recurrence (PZ0.002) and shorter Lecture survival (PZ0.002) compared with fungating/ulcerofungating type cancer, and it was consistent in rectal cancer subgroup. In the subgroup analysis by stage, survival ID: 3520791 difference concerning gross tumor morphology was more prominent in stage II patients group. In multivariate Cox regression, gross tumor morphology (hazard COLONOSCOPY RESULTS AFTER A POSITIVE STOOL ratio 1.525, confidence interval 1.059 2.198) was independent prognostic factors for DNA TEST: EXPERIENCE FROM A COMMUNITY survival. Conclusion: Our data indicate that gross tumor morphology with flat/ul- SCREENING POPULATION ceroinfiltrative type is independent prognostic factors for poor survival in non- Saumya Patel*, Sarah Grace Bowyer, Joseph J. Vicari, Aaron Shiels, metastatic colon cancer. This prognostic difference was more prominent in stage II Brad Bowyer, Chandrashekhar Thukral, Ilche T. Nonevski, Sunil Patel, colon cancer patients. Matthew W. Stier Introduction: Colonoscopy remains the gold standard screening test for colorectal cancer. Recently there has been increased use of mt-sDNA testing, a Tier 2 screening test, in the community setting. Few studies have evaluated the performance of mt-sDNA in clinical practice. This study evaluates colonoscopy findings in patients presenting after a positive mt-sDNA test in relation to a screening population. Methods: Medical records at a high-volume community GI practice were queried for colonoscopies from 2016-2020 with an indication of “positive mt-sDNA” and “screening colonoscopy”. Baseline patient demographics and procedural data were extracted. Exclusion criteria included prior adenoma, family history of colon cancer, secondary indication for GI symptoms, history of IBD, inadequate bowel preparation and incomplete procedure. Statistical analysis was performed via Chi- Square or Two-Sample t-test. Results: Mt-sDNA was ordered inappropriately for 68/ 440 (15%) patients: 32 with prior adenoma, 13 with secondary indications, and 23 with a family history of colorectal cancer. 348 patients with a positive mt-sDNA test and 446 screening colonoscopy patients were included. mt-sDNA patients were older than the screening cohort (64.7 vs 59.2 years, pZ2.78E-20) and contained more female patients (63.8% vs 54.0%). Scope withdrawal time was longer in patients with a positive mt-sDNA test (15.7 vs 13.3 min, pZ9.2E-7). In the positive mt- sDNA cohort, 33.9% (118) of patients had no adenomas, 33.62% (117) non-advanced adenomas only, 30.46% (106) advanced adenomas, and 2.01% (7) colorectal cancer. When compared to the screening colonoscopy cohort, patients presenting after a positive mt-sDNA test were more likely to have an advanced adenoma (30.5% vs 7.6%, pZ5.38E-17) or cancer (2.0% vs 0.22%, pZ.012), and were less likely to have no adenomas (33.9% vs 50.5%, pZ.3.03E-06). Screening colonoscopy detected more non-advanced adenomas (41.7% vs 33.6%, pZ.019). Adenoma detection rate was higher in those with a positive mt-sDNA test (66.0% vs 49.6%, pZ3.03E-6). Patients with a positive mt-sDNA test and no adenomas were more likely to have diverticulosis (46.04% vs 41.78%, pZ.028) or hemorrhoids (30.94% vs 24.44%, pZ.019). Conclusion: Two thirds (67%) of patients undergoing colonoscopy for a positive mt-sDNA test were found to have no adenomatous polyps or low-risk adenomas only. 2% of patients with positive mt-sDNA testing had colorectal cancer. Mt- sDNA testing was ordered inappropriately in 15% of patients referred for follow up colonoscopy. Additional education regarding appropriate use and interpretation of mt-sDNA testing is needed in the primary care setting.

Table 1. Baseline Characteristics {CEA : Carcinoembryonic antigen ; yNeoadjuvant or Adjuvant therapy (chemotherapy or radiotherapy)

Table 2. Multivariate Cox regression

www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB95 Abstracts

semi-annual audit for ADR-ESS1, but less substantially for ADR (Fig 2). ADR-ESS1 and ADR were both relatively stable year-to-year, except for endoscopists with the lowest colonoscopy volumes. Conclusions: A simple aggregation of the four major preventive colonoscopy indications into the ADR-ESS score yields a more precise and stable metric than the classic ADR based only on ﬁrst time screens, without requiring changes to detection benchmarks. Beyond increasing the colonoscopy volume available for audit, ADR-ESS has the added advantage of emphasizing quality assurance across the range of CRC control indications.

Fig 1. ADR-ESS and ADR conﬁdence intervals and endoscopist ranking

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Lecture

ID: 3524139 MONITORING COLONOSCOPY QUALITY ACROSS THE SPECTRUM OF CANCER CONTROL INDICATIONS: THE ADR-ESS (ADENOMA DETECTION RATE – EXTENDED TO ALL SCREENING AND SURVEILLANCE) SCORE Uri Ladabaum*, Ajitha Mannalithara Background: The adenoma detection rate (ADR), strictly based on first-time Fig 2. Stability of ADR-ESS vs. ADR quarter-to-quarter and semester-to- screening colonoscopies, is the best validated colonoscopy quality metric. Audit- semester ing other colonoscopy indications could increase sample size per endoscopist and improve the precision of ADR estimates and their stability over time, as well as emphasize quality across the spectrum of preventive colonoscopies. Aims: To develop the aggregate ADR-ESS (ADR extended to all screening and surveillance) score and assess its precision and stability vs. ADR. Methods: Data were SATURDAY, MAY 22, 2021 extracted for 15,253 colonoscopies by 35 endoscopists in the Stanford Colonoscopy Colon and Rectum 1 Quality Assurance Program for Oct,2017–Jan,2020. Two versions of ADR-ESS were Lecture explored: ADR-ESS1 was a simple aggregation of preventive colonoscopies (first screening, subsequent screening, surveillance, family history of colorectal neoplasia), and ADR-ESS2 included normalization of rates with respect to first ID: 3524342 screening and weighting of indications based on the proportions of an endoscopist’s IMPACT OF COVID-19 PANDEMIC ON COLORECTAL colonoscopies. We compared ADR-ESS1 vs. ADR-ESS2 vs. ADR by endoscopist with CANCER SCREENING WHEN COLONOSCOPY IS THE respect to width of confidence intervals (CI), endoscopist ranking, and stability over time and colonoscopy volume. Results: Relative to first screening, adenoma detec- DOMINANT SCREENING MODALITY tion rates were lower for subsequent screening (RR 0.80, 95%CI 0.74-0.87) and Gabrielle Waclawik*, Mark Benson, Patrick Pfau, Jennifer Weiss family history (RR 0.84, 95%CI 0.74-0.96) and higher for surveillance (RR 1.22, 95%CI Background: The COVID-19 pandemic led to a temporary cessation of elective pro- 1.15-1.31). Colonoscopy volumes for ADR-ESS were 3.4-fold (range 2.0-7.9-fold) cedures throughout the country and a dramatic decrease in screening colonoscop- higher than for ADR. The quintiles for ADR were <27%, 27 to <35%, 35 to <38%, 38 ies. It is unknown if the COVID-19 pandemic affected all CRC screening modalities to <44% and 44% vs. quintiles for ADR-ESS1 of <32%, 32 to <35%, 35 to <39%, 39 equally and overall screening rates. Aim: To determine CRC screening rates during to <43% and 43%, and for ADR-ESS2 of <31%, 31 to <35%, 35 to <40%, 40 to the COVID-19 pandemic in a large unified health system where colonoscopy is the <43% and 43%. The CIs for ADR-ESS1 and ADR-ESS2 were substantially narrower dominant screening modality. Methods: Billing and electronic medical record (EMR) than for ADR; the numerical ranking of endoscopists by ADR-ESS1 vs. ADR-ESS2 data was collected to determine the number of CRC screening tests completed by were very similar, but differed somewhat from ranking by ADR (Fig 1). modality over 15 months (July 2019–Sept 2020). Data collection was limited to age Endoscopists’ ADR-ESS1 showed less variability by quarter than ADR (Fig 2). appropriate patients (50-75 years). CRC screening test completion was determined Quarter-to-quarter fluctuations in ADR-ESS1 were minimal for endoscopists with by CPT codes for (a) fecal occult blood test (FIT/gFOBT), (b) multitarget stool DNA, 500 total colonoscopies. Period-to-period variability decreased substantially with

AB96 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts

(c) flexible sigmoidoscopy, (d) CT colonography, and (e) colonoscopy. Two sample the simethicone group (51.1% vs. 41.3%, p Z 0.019, NNT Z 11); however, left colon t-test was performed by modality to compare average monthly procedures for the PDR was similar between groups (43.3% vs. 38.9%, p Z 0.286, NNT Z 23). ADR was months pre- and post-initial COVID surge. In addition, reasons for endoscopy higher in the simethicone group (56.3% vs. 45.6%, p Z 0.011, NNT Z 10), whereas cancellation were reviewed from the EMR for July 2020-Oct 2020. Results: In 2019, the two groups had similar SADR (13.3% vs. 10.7%, p Z .341, NNT: 39) and AADR overall CRC screening rates for the unified health system were 84.5% (NZ61,410/ (14.1% vs. 13.4%, p Z .822, NNT Z 143). The PDR improved for 5 out of 6 providers 72,248) with colonoscopy as the dominant screening choice (73%). On average from but the difference was not statistically significant for individual provider, table 1. July 2019-Feb 2020, 1,641 screening colonoscopies were performed per month. In Limitation: Small sample size. Adherence to simethicone could not be assessed. Mar-Apr 2020, the monthly average dropped to 481 colonoscopies, a 70% decrease Conclusion: Adding simethicone to bowel prep improves polyp and adenoma detec- compared to pre-COVID screening [t(8)Z9.3, p<0.00001]. In May 2020, pre-pro- tion, especially in right colon. To best of our knowledge, this is first study showing cedure COVID testing was instituted (nasal swab rapid test performed within 72 hrs improvement colonoscopy quality with simethicone use in real word clinical prac- prior to procedure) and in the following months the number of screening colo- tice. We continue to review data on additional patients to strengthen the study noscopies increased to an average of 1,174 per month. This was a significant in- observations. crease from the procedures in Mar-Apr 2020 [t(5)Z2.9, pZ0.034], but remained significantly lower than pre-COVID screening [t(11)Z4.5, pZ0.001]. We saw a similar drop in use of our most common non-invasive screening test (multitarget stool DNA), as well as a similar rebound after the initial COVID surge. Use of all other modalities which were much less frequent pre-COVID remained stable (Figure 1). A total of 341 endoscopic procedures were canceled between July 2020-Oct 2020 even after pre-procedure COVID testing, 43% were due to COVID-related reasons. Conclusions: 1) The COVID-19 pandemic significantly affected CRC screening with both invasive (colonoscopy) and non-invasive (multitarget stool DNA) tests. 2) In a system with high overall CRC screening rates (>80%) with colonoscopy as the dominant CRC screening modality, procedure volume was able to resume at 72% pre-COVID monthly averages after institution of strict pre-procedure COVID screening and testing. 3) Even with an increase in colonoscopy screening after the initial COVID surge, patient cancellation due to COVID-related reasons remains high.

Figure 1. CRC screening test completion by modality (July 2019-Sept 2020)

SATURDAY, MAY 22, 2021 Colon and Rectum 1 Lecture SATURDAY, MAY 22, 2021 Colon and Rectum 1 ID: 3524600 Lecture EFFECT OF INCORPORATING SIMETHICONE IN BOWEL PREP ON POLYP AND ADENOMA DETECTION RATE IN ID: 3519117 NON-CLINICAL TRIAL SETTING IRRIGATING ACETIC ACID SOLUTION DURING Ram G. Gorantla*, Subhash Chandra, Ryan W. Walters, William Reiche, COLONOSCOPY FOR THE DETECTION OF SESSILE Anna L. Cheek, Omar Alaber SERRATED NEOPLASIA: A RANDOMIZED CONTROLLED Background: Simethicone’s antifoaming properties have potential to improve mucosal visualization during colonoscopy. Here, we evaluate effect of incorpo- TRIAL rating simethicone in bowel preparation on polyp and adenoma detection rate. George Tribonias*, Angeliki Theodoropoulou, Konstantinos G. Stylianou, Methods: In July 2018, we added simethicone 100 mg 2 tablets with last cup of split- Ioannis Giotis, Afroditi Mpitouli, Dimitrios Moschovis, Yoriaki Komeda, bowel prep in our academic practice. We included consecutive average risk adults Margarita-Eleni Manola, Grigorios Paspatis, undergoing screening colonoscopy, between July 2019 to Sept 2019 as intervention Maria TzouvalaBackground and Aims: Misdiagnosed sessile serrated arm and April 2019 through June 2018 as historical control arm. Average risk was lesions (SSLs) are important precursors for interval colorectal cancers. We fi de ned based on lack of family history for colorectal cancer and personal history of investigated the usage of acetic acid (AA) solution for improving the adenoma. Outcomes assessed were polyp detection rate (PDR), adenoma detection rate (ADR), sessile serrated adenoma detection rate (SADR) and advanced adenoma detection of SSLs in the right colon in a randomized controlled trial. detection rate (AADR). Results: A total of 568 average risk colonoscopies performed Methods: A tandem observation of the right colon was performed in 412 consecutive fi fi by 6 providers were included. Overall PDR was 68.2% in simethicone group versus patients. A rst inspection was performed under white light high-de nition endos- 57.1% in controls (p Z 0.0064, NNT Z 10), figure 1. Right colon PDR was higher for copy. In the AA group, a low concentration vinegar solution (AA: 0,005%) was irri- gated by a water pump in the right colon and it was compared with a plain solution www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB97 Abstracts of normal saline (NS) in the diagnostic yield of SSLs during the second inspection. competence (111.8 66.3 CSP; video feedback 122 77.3 vs control 91.5 53). In Secondary outcomes in overall polyp detection were measured. Results: Qualitative contrast, polyp retrieval had the greatest number of trainees reach competence comparisons showed significant differences in the detection rates of all polyps (nZ13, 59%), after 62.5 59.6 polyps; followed by optimizing the polyp view (nZ9, except adenomas, with remarkable improvement in the demonstration of advanced 40.9%). Of the 22 trainees, only 2 (9%), both in the video feedback arm, achieved (>20mm), SSLs and hyperplastic polyps during the second inspection of the right overall competence after 135 134 polypectomies. Conclusion: The learning curve colon using the AA solution. Significant improvement was also noted in the AA for CSP is steep and varied among trainees. We identified potential key steps in CSF group, as far as the mean number of polyps/patient detected, not only in SSLs (AA limiting trainee competency, including optimizing polyp position, snare positioning group: 0.14 vs NS group: 0.01, P < 0.001), but also in all histological types and all and capturing of tissue, and keeping tools close to the scope. Targeted teaching to size-categories in the right colon. Small ( 9 mm) polyps were detected in a higher specific CSP skills may accelerate skill acquisition and competence across all do- rate in the sigmoid colon expanding the effect of the method in the rest of the mains. Funded by the ASGE Endoscopy Research Award 2017 colon. Conclusion: AA assisted colonoscopy led to a significant increase in SSLs detection rate in the right colon in a safe, quick and effective manner.

SUNDAY, MAY 23, 2021 Colon and Rectum 1 Lecture

ID: 3526774 IDENTIFICATION OF THE STEPS IN COLD SNARE POLYPECTOMY THAT LIMIT OVERALL TRAINEE COMPETENCE Carmel Malvar*, Tiffany Nguyen-Vu, Rajesh N. Keswani, Swati Patel, Ravishankar Asokkumar, Yungka Chin, Matt Hall, Hazem T. Hammad, Amit Rastogi, Amandeep K. Shergill, Violette C. Simon, Alan Soetikno, Roy M. Soetikno, Sachin B. Wani, Tonya R. Kaltenbach Background: Colonoscopy with polyp detection and removal is a primary driver of the observed reductions in colorectal cancer incidence and mortality. However, there has been little focus on the training and assessment of polypectomy technique and performance. Previously, we deconstructed the cold snare polypectomy (CSP) technique into its element components to develop and validate the cold snare SUNDAY, MAY 23, 2021 polypectomy assessment tool (CSPAT). Herein, we aimed to stratify the CSPAT Colon and Rectum 1 fi domains by level of dif culty for trainees to achieve competency in CSP. Methods: As Poster part of a randomized control trial on video-based vs conventional apprentice-based feedback on CSP learning curves for senior (2nd and 3rd year) trainees rotating at 2 tertiary care centers, we video-recorded consecutive polypectomies<1cm in size. ID: 3526558 Expert raters blindly reviewed randomly assigned videos and assessed CSP perfor- ARTIFICIAL INTELLIGENCE AND COLON CAPSULE mance overall and for 12 individual domains using the CSPAT; 1-unacceptable, 2- ENDOSCOPY: AUTOMATIC DETECTION OF COLONIC sub-optimal, 3-adequate, 4-perfect. Each trainee received cumulative sum (CUSUM) learning curves at intervals of 25 CSPs. Video-feedback trainees also reviewed videos PROTUBERANT LESIONS USING A CONVOLUTIONAL of their individual CSP alongside gold standard examples. Our primary outcome was NEURAL NETWORK to rank the difficulty of CSP steps based on the number of trainees achieving Miguel M. Saraiva*, Helder Cardoso, João Afonso, João Ferreira, competence (score 3 or 4), and the number of polypectomies needed to reach Patrícia Andrade, Guilherme Macedo competence across the CSPAT domains. We collected participant, colonoscopy and I) Introduction and Objectives: Video capsule colonoscopy (CC) has established it- polyp characteristics. We determined competence using CUSUM analyses. Results: self as a possible and effective alternative to traditional colonoscopy, in selected We enrolled 22 senior trainees to our study. Baseline trainee, colonoscopy and polyp cases. Patients with a high anesthetic risk, whose colonoscopy is not possible to characteristics are shown in Table 1. Out of the 12 individual CSPAT domains, complete due to technical difficulties or patients with inflammatory bowel disease, trainee competence varied (Figure 1). No trainee achieved competence in appro- for staging and evaluation of disease activity, can use video capsule methods to priate positioning of snare over lesion as snare closed; or in ensuring appropriate assess the colonic mucosa, more conveniently and safely than with traditional co- amount of tissue is trapped within snare; and few were able to keep the tool close to lonoscopy. The protruding lesions of the colon have a wide variety of presentations the scope or ensure normal rim of tissue is resected around polyp. Moreover, the in CC images, so the development of methods for their automatic detection can be step to achieve optimal polyp position required the highest number of CSPs to reach

AB98 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts challenging. The clinical relevance of these findings is enormous, not only because SUNDAY, MAY 23, 2021 these lesions can be the source of many complications, but also because their early diagnosis is crucial. With this project, we intend to create an Artificial Intelligence Colon and Rectum 1 method capable of automatically detecting the presence of protuberant lesions in Poster the colonic lumen in CC exams, having outlined the following objectives: i) Acquisition of images containing blood and hematic traces; ii) Development of a ID: 3522787 Convolutional Neural Network (CNN); iii) Automatic identification of images containing blood or hematic traces. II) Material and Methods: A total of 24 CC exams IMPORTANCE OF OBSERVING DEPRESSED-TYPE (PillCam Colon 2) from a single-center performed between 2010-2020 were COLORECTAL NEOPLASMS IN MAGNIFYING analyzed, from which we extracted a total of 765 frames containing protuberant le- ENDOSCOPY AND ENDCYTOSCOPY sions of the colonic lumen and 2862 frames of normal mucosa. To identify the Shinei Kudo*, Yuki Takashina, Shingo Matsudaira, Kenichi Mochizuki, fi ndings automatically, these images were inserted into a CNN model with the Yuta Kouyama, Tomoyuki Ishigaki, Katsuro Ichimasa, Kenichi Takeda, transfer of learning using the TensorFlow and Keras tools. Subsequently, we evaluated the performance of the network using an independent test set. A schematic Hiroki Nakamura, Naoya Toyoshima, Masashi Misawa, Yuichi Mori, representation of the workflow used can be seen in Figure 1. III) Summary of Noriyuki Ogata, Toyoki Kudo, Tomokazu Hisayuki, Takemasa Hayashi, Results: After optimizing the different layers of the network architecture, it was able Kunihiko Wakamura, Hideyuki Miyachi, Naruhiko Sawada, to detect the presence of protuberant lesions, with an accuracy of 97.1%, 95.4% Toshiyuki Baba, Fumio Ishida sensitivity, and specificity of 97.3 %. An example of the output obtained can be seen Introduction: For colorectal carcinomas, “adenoma-carcinoma sequence” theory is in Figure 2. IV) Conclusions: We have developed a CNN for the automatic detection generally regarded as the leading factor in the development of colorectal carci- of protruding colonic lesions with high accuracy. This development of this type of nomas. In other words, colorectal carcinomas are caused by polyps. However, the tool may allow for a better evaluation of these exams, minimizing the error and time existence of depressed-type colorectal carcinomas has recently become apparent. necessary for their observation. These carcinomas are thought to emerge directly from the normal epithelium rather than at the adenomatous stage. This theory is called the "de novo" pathway. In the diagnosis of colorectal carcinomas, magnifying endoscopy (pit pattern classification) and endocytoscopy (EC classification) are useful. With these techniques, not only structural atypia but also the cellular atypia can be observed in vivo. This time, we decided to clarify the endoscopic characteristics of depressed-type colorectal carcinomas and demonstrate the validity of pit pattern and EC classification. Methods: A total of 37146 colorectal neoplasms excluding advanced cancers were resected endoscopically or surgically in our unit from April 2001 to March 2020.Of these, 29413 lesions were low-grade dysplasia, 6391 were high-grade dysplasia and 1342 were submucosally invasive (T1) carcinomas According to the developmental morphology classification, they were divided into 3 types: depressed, flat and protruded-type. We investigated the rate of T1 carcinomas and the characteristics of depressed-type neoplasms concerning pit pattern and EC classification. Result: Depressed-type lesions accounted for 62.5% of T1 carcinomas. On the other hand, the rates of T1 carcinomas with flat-type and protruding lesions were 2.8% and 2.7%, respectively. In particular, it was 10%, 0.01%, and 0% for small lesions with a diameter of less than 5 mm, respectively. Most of the flat (91.5%) and protruded- type (94.9%) lesions were type IIIL or IV, which refers to adenomas in the pit pattern classification. Most of the depressed-type lesions (92.2%) were type IIIS, VI or VN, which refers to carcinoma in the pit pattern classification. For endoscopy, most of the flat and protruding lesions were EC2, which refers to adenomas in the EC classification. In contrast, the depressed lesions were EC3a (37.0%) and EC3b (55.6%), which in the EC classification refer to invasive cancers. Conclusion: This time, we have clarified the diagnostic characteristics depressed-type lesions. Most of the depressed-type lesions were diagnosed as invasive cancer by magnifying endoscopy or endocytoscopy. In addition, since lesions tend to infiltrate the sub- mucosa regardless of size, it is important to perform magnifying endoscopy and endocytoscopy even if the lesion is small.

SUNDAY, MAY 23, 2021 Colon and Rectum 1 Poster

ID: 3521050 HOW TO DIAGNOSE TUMOR DIFFERENTIATION AS A RISK FACTOR FOR LYMPH NODE METASTASIS IN T1 COLORECTAL CANCER? Katsuro Ichimasa*, Shinei Kudo, Hideyuki Miyachi, Yuta Kouyama, Shingo Matsudaira, Kenichi Mochizuki, Yuki Takashina, Hiroki Nakamura, Tomoyuki Ishigaki, Naoya Toyoshima, Yuichi Mori, Masashi Misawa, Noriyuki Ogata, Toyoki Kudo, Tomokazu Hisayuki, Takemasa Hayashi, Kunihiko Wakamura, Toshiyuki Baba, Fumio Ishida Background: Tumor differentiation is one of the important risk factors for lymph node metastasis in T1 colorectal cancer, which is referred to in several guidelines such as US, European and Japanese. If poorly differentiated adenocarcinoma, signet- ring cell carcinoma or mucinous carcinoma are observed during histological evaluation of the endoscopically resected specimens, intestinal resection with lymph node dissection is recommended as an additional treatment. However, the way to diagnose the tumor differentiation is different among these guidelines (least differentiation in US guidelines, predominant differentiation in Japanese guidelines). The aim of this study is to determine which is more effective method in risk strat- iﬁcation of lymph node metastasis, predominant or least differentiation analysis. Methods: We initially evaluated the consecutive 853 patients with T1 colorectal cancer who underwent initial or additional surgical resection with lymph node dissection from 2001 to 2019 at our institution, for inclusion in this retrospective study. We then excluded those who had (a) synchronous or metachronous www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB99 Abstracts advanced cancer, (b) invasion to the muscularis propria or deeper in surgical specimens, (c) familial adenomatous polyposis, Lynch syndrome or ulcerative colitis, (d) preoperative chemotherapy or radiotherapy, or (e) missing data. Finally, we enrolled 805 patients in this study. We evaluated tumor differentiation in two methods (predominant or least) and divided into low-risk (well or moderately differentiated adenocarcinoma, or papillary adenocarcinoma) and high-risk (poorly differentiated adenocarcinoma, signet-ring cell carcinoma or mucinous carcinoma) in each method. The correlation between two patterns of differentiation analysis (predominant or least) and the rate of lymph node metastasis was investigated. Operative specimens were used as the gold standard for the presence of lymph node metastasis. Results: Lymph node metastasis was found in 9.7% (78/805). Rates of high-risk cases in predominant and least analysis were 0.7% (6/805) and 16.3% (131/805), respectively. Sensitivity, speciﬁcity, and area under the receiver operating characteristics curve for lymph node metastasis in predominant and least analysis were 2.6%, 99.4%, 0.50 and 28.2%, 85.0%, 0.56, respectively. Conclusion: Least differentiation analysis would be more reliable in predicting the risk of lymph node metastasis in T1 colorectal cancer than predominant differentiation analysis.

SUNDAY, MAY 23, 2021 Colon and Rectum 1 Poster

ID: 3522221 Figure 1. SROC curve for CCE-2 diagnosis of polyps > 6 mm. SYSTEMATIC REVIEW AND META-ANALYSIS OF COLON CAPSULE ENDOSCOPY ACCURACY FOR COLORECTAL CANCER SCREENING. AN ALTERNATIVE DURING THE COVID ERA? Marianny Sulbaran*, Wanderley M. Bernardo, Leonardo A. Bustamante-Lopez, Christiano M. Sakai, Paulo Sakai, Sergio C. Nahas, Eduardo G. De Moura Background and Aim: Compliance to colorectal cancer screening remains suboptimal. Barriers that limit patient’s adherence to colonoscopy screening have grown during Covid-19 pandemic. Less invasive technologies, such as colon capsule endoscopy may serve as an alternative approach.The aim of this study is to determine the diagnostic accuracy of colon capsule endoscopy compared to colonoscopy for colorectal cancer screening. Methods: A systematic review and meta-analysis of studies in which the outcomes of colonoscopy and second generation colon capsule endoscopy (CCE-2) for screening of asymptomatic patients older than 50 years oldwere compared. The primary outcomes were sensitivity, specificity, positive and negative likelihood ratios for polyps and adenomas larger than 6mm and 10mm. Results: There were 6 full-text studies that evaluated 1312 patients included for systematic review. Of these, 695 (53%) patients participated of an opportunistic program. The pooled outcomes of CCE-2 for polyps larger than 6mm were: Sensitivity: 0.87 (95% confidence interval: 0.825 – 0.908), with heterogeneity 3.69 (p Z 0.29), inconsistency Z 18.8%; Specificity: 0.94 (95% confidence interval: 0.92 – 0.96), with heterogeneity 24.05 (p Z 0.001), inconsistency Z 87.5%; Positive likelihood ratio: 11.11 (95% confidence interval: 3.7 – 33.32), with heterogeneity 34.13 (p Z 0.001), inconsistency Z 91.2%; Negative likelihood ratio: 0.15 (95% confidence interval: 0.11 – 0.2), with heterogeneity 1.9 (p Z 0.59), inconsistency Z 0.1%. The pooled outcomes of CCE-2 for polyps larger than 10mm were: Figure 2. SROC curve for CCE-2 diagnosis of polyps > 10 mm. Sensitivity: 0.86 (95% confidence interval: 0.78 – 0.92), with heterogeneity 0.62 (p Z 0.7), inconsistency Z 0.1%; Specificity: 0.98 (95% confidence interval: 0.96 – 0.99), with heterogeneity 3.08 (p Z 0.22), inconsistency Z 35%; Positive likelihood ratio: 35.45 (95% confidence interval: 19.54 – 64.34), with heterogeneity 3.36 (p Z 0.31), inconsistency Z 15.2%; Negative likelihood ratio: 0.15 (95% confidence interval: SUNDAY, MAY 23, 2021 0.09 – 0.23), with heterogeneity 0.53 (p Z 0.77), inconsistency Z 0.1%. The area under the curve of the summary receiver operating characteristic curve for Colon and Rectum 1 polyps larger than 6 and 10mm was 0.95 and 0.94 respectively (Figure 1 and 2). The Poster only cancer missed by complete CCE-2 was shown at multiple frames in the unblinded review. In total, 122 (9.3%) patients presented mild adverse events mostly ID: 3523488 related to bowel preparation. Conclusion: CCE-2 is an accurate and safe screening alternative for colorectal neoplasia, and its application may potentially improve ac- BLOOD TEST INCREASES COLORECTAL CANCER cess to screening, facilitating the detection of early colorectal lesions. SCREENING UPTAKE IN INDIVIDUALS WHO HAVE DECLINED COLONOSCOPY AND FECAL IMMUNOCHEMICAL TESTING: A RANDOMIZED CONTROLLED TRIAL Peter S. Liang*, Anika Zaman, Anne M. Kaminsky, Yongyan Cui, Gabriel Castillo, Craig T. Tenner, Scott E. Sherman, Jason A. Dominitz Introduction: The only FDA-approved blood test for colorectal cancer screening, which detects methylated SEPT9 DNA, is indicated for those who have declined first-line screening tests. However, the impact of this test on screening uptake in this screen-resistant population is unknown. We conducted a randomized controlled trial to compare outreach with re-offer of colonoscopy and fecal immunochemical test (FIT) alone (control) vs. adding the option of a blood test (intervention) in individuals who have previously declined colonoscopy and FIT. Methods: Screen-eligible Veterans aged 50-75 years with documented refusal to colonoscopy and FIT within the previous six months were randomized 1:1 to the intervention and control

AB100 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org Abstracts groups. Outreach consisted of a mailed letter followed by up to five calls. The SUNDAY, MAY 23, 2021 control group was informed of being overdue for screening and was recommended to undergo colonoscopy or FIT as first-line options. The intervention group received Colon and Rectum 1 the same information, but was also told that if they declined colonoscopy and FIT, a Poster blood test would be available as an option. Those who preferred colonoscopy or FIT were referred for testing. The primary outcome was the proportion who received ID: 3521853 any screening within six months of outreach. The secondary outcome was the proportion who completed a full screening strategy (i.e., including colonoscopy for CLINICAL AND PATHOLOGICAL CHARACTERISTICS OF those with a positive FIT or blood test) within six months. Results: In total, 359 DEPRESSED-TYPE COLORECTAL NEOPLASMS patients completed six months of follow-up. For the primary outcome, screening Shinei Kudo*, Kazumi Takishima, Yuta Kouyama, occurred in 19 of 178 (10.7%, 2 colonoscopy, 17 FIT) in the control group and 33 of Katsuro Ichimasa, Naoya Toyoshima, Yuichi Mori, Masashi Misawa, 181 (18.2%, 5 colonoscopy, 17 FIT and 11 blood test) in the intervention group Toyoki Kudo, Noriyuki Ogata, Tomokazu Hisayuki, Kunihiko Wakamura, Z (P 0.04). Test positivity was 8.8% for FIT and 18.2% for the blood test. For the Takemasa Hayashi, Toshiyuki Baba, Fumio Ishida secondary outcome, 10.1% of the control group and 15.5% of the intervention group Abstract body: Colorectal neoplasms are divided into three morphological types: completed a screening strategy (PZ0.13). Four of five patients with positive FIT or depressed-type, flat-type and protruded-type. We aimed to investigate clinical and blood tests did not complete colonoscopy within six months of outreach. In a pathological characteristics and long-term prognosis of depressed-type colorectal COVID-related sensitivity analysis that excluded patients whose initial outreach neoplasms, considered as “de novo” pathway, which is considered to emerge occurred within six months of the first confirmed case in our city, 15 of 157 (9.6%) in directly from normal epithelium, not through the adenomatous stage. Method: A the control group and 32 of 161 (19.9%) in the intervention group completed any total of 37,146 colorectal neoplasms excluding advanced cancers were resected screening (PZ0.01). Conclusions: Among screen-resistant individuals who have endoscopically or surgically in our center from April 2001 to December 2019. Of previously declined colonoscopy and FIT, offering a blood test as a secondary option these, 1,342 lesions were T1 carcinomas. According to the developmental increased screening by 8%. Importantly, there was no decrease in colonoscopy or morphology classification, they were divided into 3 types: 294 lesions (21.9%) were FIT use in those given the blood test option. These results suggest that a subset of depressed-type, 481 lesions (35.8%) were flat-type and 566 lesions (42.1%) were those who have declined first-line screening options may be receptive to a blood protruded-type. We analyzed the pathological difference of these lesions. Results test. Since the majority of participants remained unscreened, additional interven- and Discussion: Among T1 carcinomas, the rates of vessel invasion were 48%, 22% and tions are needed to encourage screening. Ensuring diagnostic evaluation after a 21%, that of poorly differentiated or mucinous adenocarcinoma was 16%, 10% and 14%, positive non-invasive test also remains a challenge and priority. that of massively submucosal invasion was 94.5%, 71.3% and 77.5%, and that of tumor budding was 34.5%, 14.8% and 16.9%, respectively. The rates of these pathological factors were significantly higher in depressed-type lesions than other types. On the other hand, the rate of adenomatous component was 5.1%, 56.7% and 51.5%, and the rate of polypoid growth was 13.8%, 57.4% and 96.4% respectively. It was significantly lower in depressed-type lesions, suggesting that they emerge directly from normal epithelium without going through the adenomatous stage. The rates of lymph node metastasis were 8.7%, 3.1% and 10.2%, respectively, in which no significant difference was found in these three types. The rate of distant metastasis or recurrence was 1% (10/ 1,342). Among these 10 cases, 5 cases were depressed-type lesions among which one showed a para-aortic lymph node metastasis and four showed a lung metastasis. Conclusions: Depressed-type colorectal neoplasms contained malignant clinical and pathological characteristics. Detection and precise diagnosis of depressed-type colorectal neoplasms is important in the treatment of colorectal carcinomas.

SUNDAY, MAY 23, 2021 Colon and Rectum 1 Poster

ID: 3520607 YOUNGER PATIENTS DO NOT DEVELOP HIGHER GRADE POLYPS ON SURVEILLANCE COLONOSCOPY THAN THEIR INDEX COLONOSCOPY WHEN COMPARED TO OLDER PATIENTS Joseph Mizrahi*, Kushang Shah, Adam Myer, Michelle Sheyman, Karl Meir, Katey-Rose Redhead, Olga C. Aroniadis, Deepak Desai, Grace Gathungu Introduction: Over the past several decades, the incidence of Colorectal Cancer (CRC) in the United States has been decreasing for patients older than 50, but increasing for patients younger than 50. While this trend has prompted a recent update to CRC screening guidelines to start at age 45 as oppose to 50, current colonic polyp surveillance guidelines are still based on data only from older patients. We thus sought to investigate whether existing colonic polyp surveillance guidelines are appropriate to use in younger patients who have polyps resected during colonoscopy. Methods: We performed a retrospective cohort study with patients recruited from two academic medical centers who underwent two colonoscopies with at least one polyp resected within a 10-year period. Five Risk Stratification Groups (RSG) were developed based on surveillance colonoscopy interval times recommended by the USMSTF on CRC (Table 1). RSGs were assigned to patients as determined by the size, number, and pathology of polyps resected during a patient’s colonoscopy, and changes in RSG from index to surveillance colonoscopy were compared between older and younger patients. Two separate analyses were done with age cutoffs at 45 and 50 given the recent change in guidelines. Further analysis was performed for patients whose RSG wors- ened from index to surveillance colonoscopy, as having higher grade polyps on surveillance colonoscopy compared to their index colonoscopy may signify an inappropriate surveillance interval. Results: 1895 patients were included in the final analysis, with 371 patients younger than 50 and 167 patients younger than 45. Patients younger than 50 had a higher rate of RSG worsening (31.54%) compared to those older than 50 (25.67%), but patients younger than 45 had a slightly lower rate of RSG worsening (25.75%) compared with patients older than 45 (26.92%). Multivariate regression analysis showed no significant association between RSG worsening and age at either the age 50 cutoff (ORZ1.23, 95% CI: 0.949 – 1.606) or at the age 45 cutoff (ORZ0.86, 95% CI: 0.589 - 1.253), but did find RSG worsening to be significantly associated with gender and indication for the procedure (Table 2). Conclusion: Our study suggests that younger patients, at both an age 45 and an age 50 cutoff, did not www.giejournal.org Volume 93, No. 6S : 2021 GASTROINTESTINAL ENDOSCOPY AB101 Abstracts significantly develop higher grade polyps on surveillance colonoscopy than their tients. Overall, any polyp was present in 1622 patients (29.6%), any adenoma in 1753 index colonoscopy, when compared to older patients. This would imply that despite patients (32.0%) and any advanced adenoma in 410 patients (7.5%). 2051 (37.4%) surveillance guidelines being developed based solely on data from older patients, did not regularly consume alcohol, 1162 (21.2%) consumed 0-70g/week, 1130 these same guidelines are indeed appropriate to use for younger patients in whom (20.6%) consumed 70-140g/week, 674 (12.3%) consumed 140-210g/week and 461 colonic polyps are found. As more younger patients undergo screening colonos- (8.4%) consumed >210g/week regularly. Among these groups, prevalence increased copies, more polyps are inevitably going to be found, and thus further study is linearly for any adenoma (28.8% vs. 29.7% vs. 32.6% vs. 38.0% vs. 42.1%, p<0.001) warranted regarding how to appropriately surveil this unique subset of patients. and any advanced adenoma (6.3% vs. 6.7% vs. 6.9% vs. 9.6% vs. 12.8%, p<0.001). On multivariable linear regression analyses correcting for established risk modifiers such as age, gender, BMI, family history, hypertension, diabetes, fatty liver disease, smoking, physical activity and dietary patterns, consumption of alcohol was independently associated with the presence of adenoma (adjusted Odds ratio [aOR] per 10g/week: 1.007, 95% confidence interval [CI]: 1.001-1.014, pZ0.039), and advanced adenoma (aOR: 1.011, 95%CI: 1.001-1.022, pZ0.033). Conclusion: We demonstrate an independent linear relationship between alcohol consumption and the risk for colorectal adenoma. Thus, even low or moderate amounts of alcohol might contribute to the risk profile for colorectal adenoma.

SUNDAY, MAY 23, 2021 Colon and Rectum 1 Poster

ID: 3522605 ARE WE READY TO ADOPT "DIAGNOSE-AND-LEAVE" STRATEGY: NOT SO FAST. A MULTICENTER INTERNATIONAL EXPERIENCE Dimpal Bhakta*, Jigar Patel, Carlos Cifuentes, Prithvi Patil, Asmeen Bhatt, Haydee Alvarado, Juan M. Alcívar-Vásquez, Raquel S. Del Valle, Roberto Oleas, Ricardo Badillo, Shahrooz Rashtak, Srinivas Ramireddy, Tomas DaVee, Carlos Robles-Medranda, Sushovan Guha, Nirav Thosani Background: Real-time optical assessment is increasingly utilized and recommended by guidelines. Given overall low prevalence of malignancy in small hyperplastic left-sided colon polyps, “Diagnose-and-Leave” strategy is currently under investigation as a cost- effective approach to the management of colon polyps due to its reduction in procedure time and costs related to histopathology. Methods: We conducted a prospective multicenter international trial on optical assessment of colon polyps and compared final results against histopathology as gold standard between June 2020 to November 2020. There were nine experienced gastroenterologists who performed these colonoscopies and evaluated polyps using high-definition white light endoscopy as well as i-Scan optical enhancement (i-Scan OE) technology. When a colorectal polyp was identified, each provider was asked to provide their optical diagnosis (adenoma, hyperplastic, sessile serrated) and overall confidence level (high or low). Data were prospectively collected in the electronic Redcap software. Optical assessment results were then compared against the final histopathology of the colorectal polyps. Results: A total of 339 polyps were evaluated during the study period. Final histopathology showed 227 adenomatous, 100 hyperplastic and 12 sessile serrated polyps. For adenomatous polyps, overall diagnostic accuracy was 85.9% (Range 66%-100%). When analysis was restricted to “high confidence” during optical assessment, overall accuracy increased to 88%. Overall accuracy decreased to 74% when analysis was limited to polyp size < 5 mm. In contrast to adenomatous polyps, overall diagnostic accuracy for hyperplastic polyps was very low at 64% (Range 38%-100%). Even when analysis was restricted to “high confidence”, diagnostic accuracy for hyperplastic polyp only increased to 67%. For polyps < 5 mm in size, SUNDAY, MAY 23, 2021 overall diagnostic accuracy for hyperplastic polyp was 77% and it improved to 82% when Colon and Rectum 1 optical assessment was done with high confidence. We had limited number of sessile Poster serrated polyp in this study and overall diagnostic accuracy was 58.3%. Conclusion: Our findings suggest that although experienced gastroenterologists are skilled at predicting adenomatous polyps (88% accurate with high confidence), their performance remains ID: 3525491 poor in accurately diagnosing hyperplastic and sessile serrated polyps. Adoption of ALCOHOL CONSUMPTION AND COLORECTAL “Diagnose-and Leave” strategy for < 5 mm size polyps would have resulted in non- ADENOMA - A DOSE-DEPENDENT RELATIONSHIP removal of close to 20% of possible precancerous polyps. Georg Semmler*, Sarah Wernly, Sebastian Bachmayer, Matthias Egger, Lena Schwenoha, Leonora Datz, Lorenz Balcar, Marie Semmler, Felix Stickel, Elmar Aigner, David Niederseer, Christian Datz Background and Aims: Although several lifestyle factors such as obesity, factors of the metabolic syndrome, physical activity, smoking, and consumption of red meat have been identified as modifiable risk factors for colorectal adenoma and colorectal cancer, the role of alcohol consumption remains controversial. Specifically, low or moderate levels have been considered “safe” due to inconclusive results from published studies. We therefore aimed to clarify the role of alcohol consumption on the prevalence of colorectal lesions. Methods: 5478 patients undergoing colonoscopy were included as part of a colorectal carcinoma colonoscopy screening program. Patients were characterized using biochemical and metabolic parameters. Data on alcohol consumption was extracted from detailed food frequency questionnaires and denoted as gramm (g)/week. For group comparison, patients were stratified according to their alcohol consumption into 0g/week, 0-70g/week, 70-140g/week, 140-210g/week and >210g/week. Colorectal neoplasia were classified macroscopically and histologically as hyperplastic polyps, adenomas, advanced adenomas and colorectal cancer. Results: 53.3% of patients were male with a mean age of 58.49.6 years and a mean BMI of 27.14.7kg/m^2. The metabolic syndrome was present in 2151 (42.8%) pa-

AB102 GASTROINTESTINAL ENDOSCOPY Volume 93, No. 6S : 2021 www.giejournal.org