ANTICANCER RESEARCH 34: 423-434 (2014)

Review Targeted Agents and -containing Regimens for the Treatment of Colon Cancer

ANDREA BONETTI1, JACOPO GIULIANI1 and FRANCO MUGGIA2

1Department of Oncology, Mater Salutis Hospital-ASL 21 della Regione Veneto, Legnago, Italy; 2New York University School of Medicine and Cancer Institute, New York, NY, U.S.A.

Abstract. Oxaliplatin and fluoropyrimidines are synergic to receive 5-FU-alone, oxaliplatin-alone or the , combinations very active for the treatment of advanced leucovorin, and oxaliplatin (FOLFOX4) combination of the colorectal cancer and for the adjuvant treatment of stage III two drugs. Response rate (ORR) and time-to-progression colon cancer. Oxaliplatin-based regimens can be further (TTP) were similarly low in patients allocated to receive strengthened by the addition of a third component, either a either 5-FU-alone (0% ORR; TTP=2.7 months) or traditional drug such as or targeted agents such oxaliplatin-alone (1.3% ORR; TTP=1.6 months) while better as anti-vascular endothelial growth factor (VEGF) drugs, results were observed in the combination arm (9.9% ORR; bevacizumab and aflibercept, or the anti-epidermal growth TTP=4.6 months). In vitro data implicate the down- factor receptor (EGFR), cetuximab and panitumumab. The regulation of thymidylate synthase (TS) protein expression availabilty of all these active agents prompted several by oxaliplatin as a possible molecular mechanism for the clinical trials on different lines of treatment of advanced observed synergy (3). As front-line treatment, the FOLFOX4 colorectal cancer patients and in the adjuvant setting. regimen was tested against leucovorin and fluorouracil Clinical studies involving the administration of anti-EGFR (LV5FU2) in a randomized study which involved 420 drugs also helped identify mutations in KRAS as a negative patients, published in 2000 (4). Although patients marker for the activity of these agents. However, positive randomized to receive up-front the combination including selection criteria for targeted agents have not been oxaliplatin up-front showed a better ORR (50.7% vs. 22.3%) identified. The results of oxaliplatin-containing regimens are and a longer time-to-progression (9.2 months vs. 6 months), critically presented and discussed in this review. overall survival (OS) was not significantly improved (16.2 vs. 14.7 months). However, the median OS observed in the Evolution of Colorectal Cancer Treatment: LV5FU2 arm was about three months longer than that The Central Role of Oxaliplatin reported in the pre-oxaliplatin era, probably as a result of the introduction of oxaliplatin (or irinotecan) as a second-line As a single agent, oxaliplatin displays only a marginal treatment. In fact, in the same year, the results of two trials activity in the clinic (1), but when administered with in which patients were randomised to receive a combination fluoruracil (5-FU), the combination is highly synergistic. The of irinotecan and 5-FU or 5-FU-alone were published. 5-FU best example of this synergism comes from the three-arm was given according to different schedules: the weekly bolus phase III trial by Rothenberg et al. (2) in which patients with infusion according to Roswell Park in the USA (5), weekly advanced colorectal cancer, progressing following treatment prolonged venous infusion (PVI) (the German schedule) or with irinotecan, 5-FU and leucovorin (LV) were randomised bi-weekly combination of bolus and PVI as in the LV5FU2 in Europe (6). The irinotecan-containing arms performed statistically better regarding all investigated parameters (ORR, TTP and OS). Overall, these data prompted the head- Correspondence to: Dr. Andrea Bonetti, Department of Oncology, to-head comparison of oxaliplatin- or irinotecan-containing ASL 21 della Regione Veneto, Via Gianella 1-37045 Legnago regimens in five trials (7-11). Looking at the most important (Verona), Italy. Tel: +39 0442632624, Fax: +39 0442632469, e- mail: [email protected] parameter, OS, in three studies the two drugs tied, while in the remaining two, the oxaliplatin arms were the winners. Key Words: Unresectable advanced colorectal cancer, oxaliplatin- Building upon the 5-FU/oxaliplatin cornerstone was the based chemotherapy, targeted agents, review. addition of irinotecan in several phase I-II studies (12-23).

0250-7005/2014 $2.00+.40 423 ANTICANCER RESEARCH 34: 423-434 (2014)

Although the different schedules make any comparison patients were included. Main objectives of the study were difficult, dose-limiting toxicities observed in all trials were two-fold: (i) non inferiority of XELOX vs. FOLFOX4; (ii) diarrhea and neutropenia. Response rates ranging from 50% bevacizumab plus chemotherapy (FOLFOX4 or XELOX) to 72% were observed in advanced colorectal cancer when superiority to chemotherapy plus placebo. The primary triplets were administered as first-line treatment, and from parameter of efficacy was progression-free survival (PFS): it 24% to 27% in the studies evaluating triplets in 5-FU- was similar in both arms (8.5 months in the FOLFOX4 plus refractory patients (13, 22). placebo or bevacizumab arms, 8 months in the XELOX plus The front-line administration of a triplet, compared to a placebo or bevacizumab arms). OS was also very close (19.6 doublet including 5-FU and irinotecan, has been investigated months in the FOLFOX 4 arms, 19.8 months in the XELOX in two randomised phase III trials. In the trial by the Hellenic arms). Capecitabine is, therefore, non-inferior to bolus and Cooperative Group which involved 283 patients, although all continuous-infusion 5-FU. Regarding the second main the investigated parameters of efficacy were in favour of the objective, the superiority of bevacizumab to placebo, triplet arm (ORR 43% vs. 34%; TTP 9.4 vs. 6.9 months; OS although the primary objective was met since a longer PFS 21.5 vs. 19.5 months), none reached statistical significance was observed in the bevacizumab arms (9.4 vs. 8 months, (23). The second trial included 244 patients and was p=0.023), the results were inferior to that observed when performed by the Italian Gruppo Oncologico Nord Ovest bevacizumab was added to 5-FU/LV alone (27) (8.8 months (GONO) Cooperative Group (24). In this study the in the FU/LV/bevacizumab group, 5.6 months in the FU/LV administration of the triplet was associated with improved group; p<0.001), to irinotecan, leucovorin and fluorouracil ORR (60% vs. 34%, p<0.001) longer OS (22.6 vs. 16.7 (IFL) (28) (10.6 months in the IFL/bevacizumab arm, 6.2 months, p=0.032) and an increased resectability rate (15% months in the IFL arm; p<0.001) or when combined with vs. 6%, p=0.033). While the 5-FU-irinotecan regimen was FOLFOX in patients progressing following treatment with the same in both trials, the schedule and the doses of the IFL (see above). Furthermore, in a planned subset analysis, drugs in the triplet arms were different. This fact, along with statistical superiority of bevacizumab vs. placebo was evident differences in the treated populations may account for the in the XELOX subgroup Hazard Ratio (HR)=0.77; 97.5% discrepant results observed. Alternative combinations such Confidence Interval (CI)=0.63 to 0.94; p=0.0026), but did as rapid sequences of doublets [e.g. oxaliplatin, irinotecan, not reach the significance level in the FOLFOX4 subgroup 5FU and LV (FOLFIRINOX)] have shown remarkable (HR=0.89; 97.5% CI=0.73 to 1.08; p=0.1871). Finally, ORR activity against . was identical (38%) in patients who received bevacizumab or placebo, while OS was only marginally-improved in Adding anti-Angiogenic Antibodies to patients treated with chemotherapy plus bevacizumab (21.3 Oxaliplatin-based Regimens vs. 19.9 months p=0.07) (31); OS was 20.3 months in the FOLFOX placebo arm vs. 21.2 months in the FOLFOX Bevacizumab is a monoclonal antibody that blocks the bevacizumab arm (HR=0.94; 95% CI=0.75-1.16) and 19.2 vascular endothelial growth factor, a critical mediator of (XELOX placebo) vs. 21.4 (XELOX bevacizumab) angiogenesis (25, 26). Randomized studies in previously (HR=0.84; 95% CI=0.68-1.04) (31, Appendix online only). untreated patients have shown that the addition of NO16966 updated results, showed that median OS was 19.8 bevacizumab to 5-FU alone (27) or to the combination of 5- months in the pooled XELOX/XELOX-placebo/XELOX- FU and irinotecan (28) improves the efficacy of bevacizumab arms vs. 19.5 months in the pooled chemotherapy. In patients previously treated with 5-FU and FOLFOX4/FOLFOX4-placebo/FOLFOX4-bevacizumab irinotecan, the inclusion of bevacizumab into the FOLFOX4 arms (HR=0.95, 97.5% CI=0.85-1.06); in the pooled regimen significantly improved ORR (22.7% vs. 8.6%), TTP XELOX/XELOX-placebo arms, median OS was 19.0 vs. (7.3 vs. 4.7 months) and OS (12.9 vs. 10.8 months), when 18.9 months in the pooled FOLFOX4/FOLFOX4-placebo compared to the FOLFOX-only arm (29). The study arms (HR=0.95, 97.5% CI=0.83-1.09) (32), confirming the NO16966 began as a front line study in which patients were primary analysis. randomized to receive either FOLFOX4 or XELOX Having previously shown the superiority of the three-drug (oxaliplatin at 130 mg/m2 as an intravenous injection on day combination with irinotecan, oxaliplatin, leucovorin and 1 and capecitabine at 1,000 mg/m2 orally b.i.d on days 1-14 fluorouracil (FOLFOXIRI) over the two-drug combination every three weeks) (30, 31). In August 2003, after the phase FOLFIRI (24), the GONO group recently reported the III bevacizumab data became available, the protocol was conclusion of the TRIBE trial a two-arm protocol in which amended to a 2×2 partially blinded study by adding bevacizumab was added to either FOLFOXIRI or FOLFIRI 7.5 mg/kg of bevacizumab i.v. or placebo on day 1 every (33). In this study, the three-drug arm was associated with a three weeks to XELOX and bevacizumab 5 mg/kg i.v. or statistically significant improvement of PFS (12.2 vs. 9.7 placebo every two weeks to FOLOFOX4; overall 2,034 months) and ORR (65% vs. 53%). However, the increase of

424 Bonetti et al: Oxaliplatin-containing Regimens for the Management of Colorectal Cancer response rate did not translate into improved resection of was tested in another smaller phase III study (BEBYP), in liver metastases in the whole population (15% vs. 12%) and 185 patients (39). This study had planned to enroll 262 in the subgroup of patients with liver-only metastases (32% patients but was closed prematurely following the vs. 28%). presentation of the TML results. The primary end-point was In spite of the negligible benefits observed when PFS that was longer in the bevacizumab compared to the bevacizumab was added to oxaliplatin-based regimens in the placebo arm (5.2 vs. 6.7 months; p=0.007). ORR was 18% in front-line setting, bevacizumab is commonly included in the placebo arm and 21% in the bevacizumab arm (p=0.71); these regimens following the hypothesis that it is survival data are still immature but similar in the two arms fundamental in order to normalize the abnormal structure and (16 vs. 16.5 months; p=0.34). function of tumor vasculature to make it more efficient for Finally the concept of keeping the anti-vascular agent oxygen and drug delivery to cancer cells (34). Further upon progression was studied in another randomised phase corollaries from this hypothesis have lent support to the use III trial, the VELOUR trial, in which patients with metastatic of bevacizumab as maintenance following front-line colorectal cancer progressing on first-line oxaliplatin-based treatment and also upon progression, changing the chemotherapy with or without bevacizumab (n=1226) chemotherapy partners since resistance to chemotherapy received either FOLFIRI alone or FOLFIRI plus the anti- results from changes in tumour cell biology and is often vascular agent aflibercept (40). The observed gain in OS agent-specific while bevacizumab resistance, if it occurs, can (primary end-point) was similar of that observed in the TML result from the development of alternative angiogenesis trial: 13.5 months for patients receiving FOLFIRI plus pathways (35, 36). aflibercept and 12.1 months for patients receiving FOLFIRI The role of bevacizumab as a single-maintenance agent plus placebo (HR=0.82, p=0.0032), this last trial supporting was investigated in only one randomised non-inferiority the US FDA approval of aflibercept after failure of second- design aimed at demonstrating the non-inferiority of a no- line treatments. treatment strategy, compared to the administration of bevacizumab (37). Eligibility criteria for this trial requested Adding anti-Epidermal Growth Factor the inclusion of bevacizumab in an up-front regimen with an Receptor Antibodies (EGFR) to oral or intravenous fluoropyrimidine (alone or in Oxaliplatin-based Regimens combination with irinotecan or oxaliplatin). The primary end-point of the study, which included 262 patients, was TTP Cetuximab and panitumumab are monoclonal antibodies (from randomisation) while secondary end-points were PFS against the EGFR, a molecular target that is expressed in the (from the beginning of front-line chemotherapy), time-to- majorty of colorectal tumors (41). Panitumumab is a fully second line treatment, OS, adverse events and costs. TTPs human immunoglobulin (Ig) G2 monoclonal antibody (42) was 4.1 months among 124 patients randomised to receive while Cetuximab is a chimeric human-mouse IgG1 bevacizumab maintenance and 2.9 months among 123 monoclonal antibody (43); both antibodies bind the EGFR patients randomised to observation (p=0.47, i.e. non- extracellular domain with high affinity and inhibit ligand- inferiority was not demonstrated). With 168 events, OS induced EGFR tyrosine phosphorylation, tumor cell results were 25.1 months among bevacicumab-maintained activation, and tumor cell proliferation. and 22.8 months among observed patients (p=0.218). As The two drugs were initially tested as single agents, and expected, the costs of the two strategies are astonishingly in combination with anticancer drugs, in patients with different: 37,596 USD for each bevacizumab-maintained advanced colorectal cancer patients selected on the basis of patients and 8,180 USD for each observed patient. the expression of EGFR, in different lines of chemotherapy. Bevacizumab beyond progression was investigated in the Only later it did become evident that the status of KRAS was TML; ML18147, a randomised phase III trial in which 820 a better biomarker for selecting patients for a treatment with patients with advanced colorectal cancer, progressing on antibodies to EGFR. In fact, it has been shown in first-line chemotherapy plus bevacizumab, were randomised retrospective studies and in subgroup analyses from to chemotherapy-alone (switching to fluoropyrimidine plus randomised trials that clinical responses to antibodies against irinotecan or oxaliplatin, depending on the type of front-line EGFR are restricted to patients (approximately 55 to 70%) chemotherapy administered) or to chemotherapy and whose tumors are wild type for KRAS (44-52). bevacizumab (38). The primary end-point was OS from The most relevant randomised trials in which antibodies initiation of second-line chemotherapy. The primary end- to EGFR are investigated in combination with oxaliplatin- point was met with and observed OS of 11.2 months among based regimens are reported in Table I. patients who continued bevacizumab and 9.8 months among The OPUS (Oxaliplatin and Cetuximab in First-Line patients who received chemotherapy alone (HR=0.81; 95% Treatment of mCRC) was a randomised phase II study that CI=0.69-0.95, p=0.0062). Bevacizumab beyond progression compared the use of FOLFOX4 plus cetuximab (n=169) vs.

425 ANTICANCER RESEARCH 34: 423-434 (2014)

Table I. Published phase III trials evaluating the addition of cetuximab or panitumumab to oxaliplatin-based regimens in the front-line setting of advanced colorectal cancer patients.

Trial Comparative Total N KRAS evaluated KRAS ORR p-Value PFS p-Value OS p-Value regimens patients N (%) wild-type N (%) (%) (months) (months)

OPUS FOLFOX/Cetux 169 159 82 57 0.0027 8.3 0.0064 22.8 0.39 (54) FOLFOX 168 156 97 34 7.2 18.5 COIN FOLFOX/XELOX/Cetux 815 668 362 64 0.049 8.6 0.60 17.0 0.67 (55) FOLFOX/XELOX 815 648 367 57 8.6 17.9 NORDIC FLOX/Cetux 194 169 97 46 0.89 7.9 0.66 20.1 0.48 VII (56) FLOX 185 155 97 47 8.7 22.0 PRIME FOLFOX/Pmab 593 546 325 55 0.68 9.6 0.02 23.9 0.07 (57) FOLFOX 590 550 331 48 8.0 19.7 New EPOC FP + Cetuximab 137 137 117 58.4 14.1 0.03 39.1 (58) FP 134 134 116 53.7 20.5 Not reached NO16966 FOLFOX/XELOX 699 NA NA 38 NS 9.4 0.023 21.3 0.07 (32) + Bev 701 38 8 19.9 FOLFOX/XELOX TRIBE FOLFOXIRI + Bev 508 NA NA 65 0.006 12.2 0.012 NR (33) FOLFIRI + Bev 53 9.7

N=number; ORR=objective response rate; PFS=progression free survival; OS=overall survival; FOLFOX=fluorouracil, leucovorin and oxaliplatin; Cetux=cetuximab; XELOX=capecitabine and oxaliplatin; FLOX=oxaliplatin, fluorouracil, leucovorin; Pmab=panitunumab; FP=fluoropyrimidine- oxalipatin combination; FOLFOXIRI=irinotecan, oxaliplatin, leucovorin and fluorouracil; FOLFIRI=fluorouracil, leucovorin and irinotecan; Bev=bevacizumab; NA=not applicable; NS=not significant; NR=not reported.

FOLFOX4 alone (n=168) in patients with previously (43%) had KRAS mutations. In patients with KRAS wild-type untreated advanced colorectal cancer (53, 54). The primary tumours (arm A, n=367; arm B, n=362), OS did not differ objective was to determine whether the addition of the between treatment groups (median survival 17.9 months in antibody improved the ORR compared to chemotherapy the control group vs. 17.0 months in the cetuximab group; alone. Secondary objectives included the determination of HR=1.04, 95% CI=0.87-1.23, p=0.67). Similarly, there was rates of potentially curative metastasectomy, duration of no effect on progression-free survival (8.6 months in the response, PFS, OS, and safety. A retrospective subgroup control group vs. 8.6 months in the cetuximab group; analysis done on regulatory request investigated the potential HR=0.96, 0.82-1.12, p=0.60). ORR increased from 57% relationship between PFS/ORR and tumor KRAS mutational (n=209) with chemotherapy alone to 64% (n=232) with status (n=315, 93% of the whole population; KRAS wild-type addition of cetuximab (p=0.049). population n=179, 57%). In the original patient population, In the first line phase III NORDIC VII study patients were adding cetuximab improved the ORR by an absolute increase randomly assigned to receive either standard Nordic FLOX of 10% (36% to 46%), which did not reach the original goal (arm A), cetuximab and FLOX (arm B), or cetuximab [the odds ratio (OR) was 1.52]. Median PFS was identical for combined with intermittent FLOX (arm C). The primary end- both arms at 7.2 months. However, cetuximab was effective in point was PFS. OS, response rate (RR), R0 resection rate, the population with tumors that demonstrated wild-type and safety were secondary end-points (56). KRAS status was KRAS. The ORR increased from 34% to 57% (OR 2.551; assessed during conduction of the trial, but no adjustment of p=0.0027), and PFS alone improved from 7.2 to 8.3 months the sample size was performed. As a result, the number of (OR=0.567; p=0.0064). The observed OS did not differ patients in the two main comparison arms, FLOX with significantly between the two groups: 18.5 months with cetuximab and FLOX without cetuximab, with KRAS wild- FOLFOX alone; 22.8 months with FOLFOX plus cetuximab type tumours was 97 per arm, which clearly diminishes the (p=0.39). Remarkably, in the KRAS-mutant population, the power of the trial. OS was almost identical for the three ORR, median PFS, and overall PFS were markedly worse for groups (20.4, 19.7 and 20.3 months, respectively), and patients who received cetuximab. confirmed response rates were 41%, 49%, and 47%, The COIN trial enrolled 1,630 patients with advanced respectively. In patients with KRAS wild-type tumours, colorectal cancer, randomised to receive a combination of cetuximab did not provide any additional benefit compared fluoropyrimidine and oxaliplatin with (arm B) or without with FLOX-alone. In patients with KRAS mutations, no (arm A) cetuximab (55). Tumour samples from 1,316 (81%) significant difference was detected, although a trend toward patients were used for somatic molecular analyses; 565 improved PFS was observed in arm B.

426 Bonetti et al: Oxaliplatin-containing Regimens for the Management of Colorectal Cancer

Table II. Randomised studies evaluating oxaliplatin-based combinations as adjuvant treatment for colon cancer.

Trial Comparative Total N KRAS Disease 3-year p-Value 3 year p-Value OS p-Value regimens patients evaluated stage DFS DFS (months) N wt stage II stage III Stage III

MOSAIC LV-5FU2 2246 NA II/III 79.9** 0.26 58.9** 0.005 68.7§ 0.023 (64) FOLFOX 83.7 66.4 72.9 NSABP CO7 Roswell Park 2409 NA II-III 89.6** 57.8 73.8** 0.052 (65) Roswell Park + 89.7 64.4 76.5 Oxaliplatin XELOX (74) Bolus 5FU/LV 1886 NA III NA 66.5 0.0045 74.2 0.15 Capecitabine + 70.9 77.6 Oxaliplatin AVANT (79) FOLFOX 3451 NA II-III NR 76 85 FOLFOX Bevacizumab 74 0.07 81 0.02 XELOX Bevacizumab 75 0.04 82 0.21 NSABP-C08 mFOLFOX6 2672 NA II-III 84.7 0.35 72.4 0.25 NR (78) mFOLFOX6 + 87.4 74.2 Bevacizumab NCCTG FOLFOX6 2686 2070 III NA 74.6 0.08 87.3 0.15 N0147 (80) FOLFOX6 + Cetuximab 71.5 85.6 PETACC FOLFOX4 2559 1602 III NA 78 0.66 NR 8 (81) FOLFOX4 + Cetuximab 75.1

Legend: **=at 5 years; §=at 6 years; N=number; wt=wild-type; DFS=disease free survival; LV-5FU2=leucovorin and fluorouracil; OS=overall survival; 5FU=fluorouracil; LV=leucovorin; FOLFOX=fluorouracil, leucovorin and oxaliplatin; NA=not applicable; NR=not reported.

The Panitumumab Randomized Trial in Combination With Committe since PFS was significantly worse in the Chemotherapy for Metastatic Colorectal Cancer to Determine cetuximab arm (14.8 vs. 24.2 months, p<0.048). Efficacy (PRIME) a randomized phase III trial designed to In conclusion, the addition of EGFR-targeting antibodies evaluate panitumumab at 6 mg/kg every two weeks plus to oxaliplatin-containing regimens for the front-line therapy FOLFOX4 (n=593) vs. FOLFOX4 alone (n=590) as a first- of patients with KRAS wild-type advanced colorectal cancer, line treatment in patients with wild-type or mutant KRAS is associated with results which were not consistently tumours (57). Among patients with wild-type KRAS tumours, observed in the reported trials. In fact, ORR increased in the the addition of panitumumab to first-line FOLFOX4 OPUS and COIN trials; PFS increased in the OPUS and significantly improved PFS (the primary endpoint; 9.6 vs. 8.0 PRIME trials. No differences in OS were observed while in months, respectively; HR=0.80; 95% CI=0.66-0.97; p=0.02) the new EPOC trials the addition of cetuximab is clearly compared with FOLFOX4 alone. Among patients with wild- detrimental. type KRAS tumours the addition of panitumumab to The findings of NORDIC are particularly intriguing since FOLFOX4 vs. FOLFOX4 alone was not associated with an it is the only trial in which patients with KRAS-mutated improvement of median OS (23.9 vs. 19.7 months, cancer experienced a trend towards improvement in PFS with respectively; HR=0.83; 95% CI=0.67-1.02; p=0.072) or with an antibody to EGFR. It is also the only trial in which the a better overall response rate (55% with FOLFOX plus observed response rate in patients with KRAS-mutated panitumumab, 48% with FOLFOX alone; OR=1.35; tumors was numerically higher than in these with KRAS p=0.068). Patients with KRAS mutant tumours who received wild-type cancer. The possible explanations for the different panitumumab plus FOLFOX4 had significantly shorter PFS results by adding cetuximab or panitumumab to oxaliplatin- than patients treated with FOLFOX4 alone (7.3 vs. 8.8 (or irinotecan)-containing regimens (not presented here) are months, respectively; HR=1.29; 95% CI=1.04-1.62; p=0.02), extensively discussed elsewhere (59). but median OS and the ORR were not significantly different. Finally, the addition of cetuximab to a fluoropyrimidine- Use of Both anti-Angiogenic and anti-EGFR oxalipatin combination was investigated in 272 patients Antibodies with Chemotherapy randomised into the NewEPOC study (58). Eligible patients were required to be KRAS wild-type and to have operable Since combining cytotoxic drugs that act through different liver metastases. The study was prematurely closed following mechanisms improved outcomes in patients with metastatic a recommendation from the Independent Data Monitoring colorectal cancer, it seemed logical that further progress

427 ANTICANCER RESEARCH 34: 423-434 (2014) would result from combining bevacizumab with either investigated in three (66-68). These trials show that while the cetuximab or panitumumab and administering these addition of oxaliplatin to the regimens including 5-FU and monoclonal antibodies together with chemotherapy. LV is associated with a better outcome for patients, the The CAIRO 2 study was a randomised phase III trial in introduction of irinotecan is either marginally effective or which 732 patients with previously untreated metastatic detrimental. Furthermore, the activity of oxaliplatin is colorectal cancer were randomly assigned to receive independent of the 5-FU-LV schedule since the results capecitabine, oxaliplatin, and bevacizumab or the same three initially observed in the MOSAIC trial in which oxaliplatin drugs accompanied by cetuximab in cycles administered is given bi-weekly with bolus and continuous infusion 5-FU every three weeks (60). After a median follow-up of 23 were confirmed in the NSABP C07 trial in which bi-weekly months, the addition of cetuximab to the combination of oxaliplatin is combined with weekly 5-FU and LV. However, capecitabine, oxaliplatin, and bevacizumab significantly the schedule issue matters in terms of toxicity, especially reduced the median PFS, from 10.7 months to 9.4 months; neurotoxicity, enteropathy and toxic death. The lower the addition of cetuximab was also associated with a trend incidence of grade III neurotoxicity reported in the NSABP towards reducing the median OS from 20.3 months to 19.4 C07 trial (8%) compared to the MOSAIC trial (12.4%) is months. Tumor tissue was assessed for the status of the easily explained by the lower cumulative doses of oxaliplatin KRAS gene in 71% of patients; mutations were found in 40% in the former study (765 mg/m2 vs. 1,025 mg/m2). The GI of the specimens. The addition of cetuximab did not improve toxicity in the NSABP C07 was described in detail (69). A the outcome in patients whose tumors contained wild-type syndrome of bowel wall injury characterised by KRAS but was deleterious for those with tumors bearing a hospitalisation for the management of severe diarrhoea or mutant KRAS gene. The negative effect of adding an dehydration and radiographic or endoscopic evidence of antibody to EGFR to a chemotherapy–bevacizumab bowel wall thickening or ulceration occurred in 79 out of combination was also observed by Hecht et al. in the 1,857 patients (4.3%). The majority of these patients (65%) Panitumumab Advanced Colorectal Cancer Evaluation had received bolus 5-FU-LV and oxaliplatin. Besides this (PACCE) trial (61), in which 823 patients who had not syndrome, not observed in the MOSAIC trial, the incidence received previous treatment for metastatic colorectal cancer of grade III and IV diarrhoea was also higher in the were randomly assigned to receive FOLFOX and oxaliplatin containing arm of the NSABP C07 trial (38% vs. bevacizumab, either alone or accompanied by panitumumab. 10.8%). Finally treatment related deaths were 0.5% in the The addition of panitumumab reduced both the median PFS MOSAIC trial and 1.2% in the NSABP C07 trial. In and the median OS. conclusion, FOLFOX should be the preferred regimen in the Finally, the concept of combining both antibodies with adjuvant setting, although the lower incidence of grade III FOLFOX or FOLFIRI was investigated in the CALGB neurotoxicity, the ease of administration of bolus delivery Intergroup study C80405 (62). This was a three-arm study and the avoidance of a central catheter could make FLOX powered for survival. The physician selected either FOLFOX preferable in some cases, with the warning that enteric or FOLFIRI, and then patients were randomly assigned to toxicity should be carefully managed. The positive results of bevacizumab alone, cetuximab alone or the combination of the MOSAIC trial, which enrolled 40% of patients with stage the two. The arm in which cetuximab and bevacizumab were II disease, led the regulatory Authorities FDA in the USA combined was closed in September 2009. Therefore, this trial and the European Medicine Agency to approve this protocol will compare cetuximab and bevacizumab head-to-head (and for the adjuvant treatment of only stage III disease. These FOLFOX vs. FOLFIRI). The results of this study are awaited decisions were criticised in a commentary by Grothey and with interest since thus far the two monoclonal antibodies Sargent (70) published in the Journal of Clinical Oncology, have been compared in combination with the FOLFIRI-only for the main reasons that were based upon a sub-group backbone, in the FIRE trial (63). analysis. The recently reported improved OS observed only in stage III in both trials (71, 72), with an absolute difference The Adjuvant Setting: Where Are We in 2013? of 4.4% (p=0.029) in the MOSAIC trial and of 2.5% in the NSABP C07 (p-value not reported) in favour of the The results obtained with the addition of oxaliplatin (or oxaliplatin-containing arm could, however, lend support to irinotecan) to the 5-FU backbone in advanced-stage disease, the conservative approach applied by the regulatory agencies. prompted the launch of a series of randomised phase III Furthermore, the observed interaction between age and studies in stage II and III colon cancer. In these studies treatment suggest to use caution recommending oxaliplatin- patients were randomised to receive either a combination of containing regimens for the elderly. In fact, updated OS 5-FU and LV or the same combination plus oxaliplatin (or results of MOSAIC and NSABP trials indicate that the gain irinotecan). The role of oxaliplatin was investigated in two is limited to patients younger than 70 years old. In particular, studies (64, 65) while the impact of irinotecan was in NSABP C07 OS significantly improved with FLOX

428 Bonetti et al: Oxaliplatin-containing Regimens for the Management of Colorectal Cancer compared with FULV for patients younger than age 70 studies have resulted in the approval of bevacizumab in (HR=0.80; 95% CI=0.68 to 0.95; p<0.013) (72). The 5-year combination with a fluoropyrimidine-, oxaliplatin-, or OS estimates were 78.8% for FULV and 81.8% for FLOX, irinotecan-based for metastatic a 3.1% improvement in patients younger than age 70 years. colorectal cancer. It was therefore anticipated that OS did not vary significantly by treatment in patients aged bevacizumab would also improve the outcome of patients 70 years (p=0.30), but nominal OS at 5 years was 4.7% with high-risk stage II and stage III colon cancer when worse for patients treated with FLOX (71.6%) compared treated with the standard infusional FOLFOX chemotherapy. with that for patients treated with FULV (76.3%) among This expectation formed the basis of the National Surgical these older patients. In the MOSAIC trial, 5-year OS was not Adjuvant Breast and Bowel Project (NSABP) C-08 and of significantly different in the elderly (n=315): 75.8% with the AVANT (AVastin adjuvANT) trials (78, 79). FOLFOX vs. 76.1% with LV5FU2 (p=0.661) (73). In the NSABP C08 study conducted in the USA stage II More recently were reported the results of NO16968 and III colon cancer 2,672 patients were randomised to either (XELOX in Adjuvant Colon Cancer Treatment [XELOXA]), FOLFOX6 alone (an evolution of FOLFOX4 in which the a randomised phase III study designed to investigate whether bolus of 5-FU on day 2 is taken off while 5-FUPVI is given the addition of oxaliplatin to an oral fluoropyrimidine, would at the dose of 2,400 mg/m2 over 46 h starting on day 1), or maintain the efficacy of treatment compared to earlier trials to the same combination plus bevacizumab 5 mg/kg for 12 offering at the same time a potentially more convenient cycles followed by bevacizumab alone at the same dose for regimen (74). In this study, oxaliplatin was combined with 12 additional cycles (78). capecitabine (XELOX) and compared with bolus FU/FA The AVANT trial is a three-arm European trial in which (Mayo Clinic or Roswell Park regimens) in patients with 3,451 stage III and high risk stage II patients were stage III colon cancer. The intention-to-treat population randomised to receive: (i) FOLFOX4 alone for 12 cycles, (ii) comprised 1,886 patients; 944 patients were randomly FOLFOX4 plus bevacizumab at 5 mg/kg for 12 cycles assigned to XELOX and 942 to FU/FA (Mayo Clinic, n=664; followed by bevacizumab alone at the dose of 7.5 mg/kg Roswell Park, n=278). After 57 months of follow-up for the every three weeks for eight additional cycles or (iii) XELOX primary analysis, 295 patients (31.3%) in the XELOX group (capecitabine oxaliplatin) plus bevacizumab at 7.5 mg/kg had relapsed, developed new primary colon cancer, or died every three weeks for 8 cycles followed by bevacizumab compared to 353 patients (37.5%) in the FU/FA group (HR alone at the same dose and interval for eight additional for DFS=0.80; 95% CI=0.69 to 0.93; p=0.0045). The 3-year cycles (79). This study addresses not only the value of DFS rate was 70.9% with XELOX and 66.5% with FU/FA. bevacizumab in this population but also the possibility of The HR for OS for XELOX compared to FU/FA was 0.87 substituting capecitabine to bolus and PVI 5-FU, thus (95% CI=0.72 to 1.05; p=0.1486). The 5-year OS for avoiding the need for a central catheter. The results show that XELOX and FU/FA were 77.6% and 74.2%, respectively. neither NSABP C08 nor the AVANT met their primary end- Although direct comparisons of oxaliplatin-based regimens point of prolonging DFS after three years. Furthermore, in in the adjuvant setting have not been performed, data from the AVANT trial the administration of bevacizumab was large phase III trials evaluating FOLFOX-4 and XELOX in associated with a detrimental effect on OS in the FOLFOX the first- or second-line treatment of metastatic colorectal arm (HR=1.27; 95% CI=1.03-1.57; p=0.02) but not in the cancer have demonstrated that XELOX is non-inferior to XELOX arm (HR=1.15; 95% CI=0.93-1.42; p=0.21). FOLFOX4 in terms of PFS, OS, and objective response rate The role of cetuximab as an addition to FOLFOX6 was (75, 76). investigated in the North Central Cancer Treatment Group Furthermore, a systematic review and meta-analysis of 40 (NCCTG) N0147 trial, a randomised phase III trial which trials comparing oxaliplatin-containing regimens to enrolled 2686 patients resected for stage III wild-type KRAS fluoropyrimidine regimens did not show any significant colon cancer (80). The primary randomized comparison was difference in DFS at a median follow-up of three-years (or 12 bi-weekly cycles of mFOLFOX6 with and without closest reported analysis) for XELOX vs. FLOX (HR=0.99, cetuximab. KRAS mutation status was centrally determined. 95% CI=0.80-1.22) or FOLFOX (HR=1.00, 95% CI=0.72- The trial was halted after a planned interim analysis of 48% 1.41) (77). There was also no significant difference in OS at of predicted events (246/515) occurring in 1,863 (out of a median follow-up of at least 5 years. In this study no 2,070 planned) patients with tumours having wild-type interaction was observed between age and treatment arm and KRAS. DFS in patients with wild-type KRAS mutations was DFS benefit was the same in the populations of patients <65 the main end-point of the study. Secondary end points or ≥65 years old. included OS and toxicity. Molecularly-targeted agents demonstrated some degrees Three-year DFS for mFOLFOX6 alone was 74.6% vs. of activity in patients with metastatic colorectal cancer and 71.5% with the addition of cetuximab (HR=1.21; 95% other advanced malignant diseases. In fact, several phase III CI=0.98-1.49; p=0.08) in patients with wild-type KRAS, and

429 ANTICANCER RESEARCH 34: 423-434 (2014)

67.1% vs. 65.0% (HR=1.12; 95% CI=0.86-1.46; p=0.38) in effect of MMR status in the response to FOLFOX adjuvant patients with mutated KRAS, with no significant benefit in chemotherapy should be assessed by the undergoing analyses any subgroups assessed. Among all patients, grade 3 or of tissue samples from previously completed randomized trials higher adverse events (72.5% vs. 52.3%; OR]=2.4; 95% comparing 5-FU plus oxaliplatin with 5-FU alone, such as the CI=2.1-2.8; p<0.001) and failure to complete 12 cycles (33% MOSAIC and NASBP-C07 studies. The underlying biological vs. 23%; OR=1.6; 95% CI=1.4-1.9; p<0.001) were mechanisms of MMR effect on adjuvant chemotherapy remain significantly higher with cetuximab. to be identified. Increased toxicity and greater detrimental differences in To summarise, in less than two decades, the three-year all outcomes were observed in patients aged 70 years or DFS for patients with stage III colon cancer increased from older with wild-type KRAS. In particular patients who were 44% with surgery alone in 1990, to 62% with the six month treated with mFOLFOX6 alone demonstrated significantly combination of 5-FU and LV in 1995, to 65% observed in better OS (HR=2.00; 95% CI=1.05-3.78; p=0.03), with a the LV5-FU2 arm in the MOSAIC trial and finally to the three-year estimate of 86.2% (95% CI=78.9%-94.1%) for the 72% obtained in both oxaliplatin-containing arms of the mFOLFOX6 alone group vs. 72.5% (95% CI=64.0%-82.0%) MOSAIC and NSABP C07 trials. Improvements in the for the mFOLFOX6 with cetuximab group. imaging which allowed a better selection of patients Similar negative results were reported in the Pan-European contributed to these results but this success story is mostly Trials in Alimentary Tract Cancer (PETACC) 8 trial in which attributable to oxaliplatin-based adjuvant chemotherapy. 2,559 patients with completely-resected colon cancer (1,602 Therefore, the USA Intergroup and the Italian TOSCA with wild-type KRAS) were randomised to receive either studies seeking a reduction in toxicity by randomizing three FOLFOX4 alone (arm A) or the same chemotherapy plus versus six cycles of FOLFOX following stage III curative cetuximab (arm B) (81). Among KRAS wild-type patients, no resection is a key matter for the future. difference in the primary end-point, three-year DFS, was observed between the two arms: 78% in arm A, 75.1% in arm Conflicts of Interest B (HR=1.05; 95% CI=0.85-1.29; p=0.66). Grade 3 or higher None declared. adverse events were significantly increased in arm B (80.9%) vs. arm A (66.2%; HR=1.09; 95% CI=0.81-1.47; p=0.56). References The results of all these studies clearly demonstrated that the addition of molecularly targeted agents to oxaliplatin-containing 1 Grothey A and Goldberg RM: A review of oxaliplatin and its regimens is not associated with an improvement of DFS/OS. clinical use in colorectal cancer. Expert Opin Pharmacoter 5: Therefore, oxalipatin-fluoropyrimidine regimens are the only 2159-2170, 2004. ones to have consistently shown a favorable impact in terms of 2 Rothenberg ML, Oza AM, Bigelow RH, Berlin JD, Marshall JL, DFS (72-74) and OS (72, 73) compared to fluoropyrimidine Ramanathan RK, Hart LL, Gupta S, Garay CA, Burger BG, Le alone. 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