Effect of Angiosonography to Monitor Response During Imatinib

Imaging, Diagnosis, Prognosis

Effect of Angiosonography to Monitor Response During Imatinib Treatment in Patients with Metastatic Gastrointestinal Stromal Tumors Ugo De Giorgi,1Camillo Aliberti,3 Giorgio Benea,3 Matteo Conti,2 andMaurizioMarangolo1

Abstract Purpose: Gastrointestinal stromal tumor (GIST) metastases are typically intra-abdominal and hypervascular. We assessed the effect of angiosonography with a second-generation contrast agent to monitor response during imatinib treatment in patients with metastatic KIT+ GIST. Experimental Design:Ten consecutive patients with known advanced KIT+ GISTwere investigated with angiosonographyand computerized tomography(CT).We also monitored the serum levels of the major angiogenic growth factor, vascular endothelial growth factor. Results: Angiosonographyshowed a reduction in tumor vascularization of liver metastases during imatinib treatment in all cases.We observed a reduction in tumor vascularization before a reduction in tumor size. The tumor perfusion appeared reduced in the central part of the liver metastases.With a median follow-up of18 months (range 3-33), a reduction in tumor vascularization was initiallyobserved in all patients, but progressive disease was documented in four patients following imatinib treatment. CTdocumented tumor response according to standardized criteria in six patients, stable disease in four, and progressive disease according to angiosonography. The reduction of tumor perfusion at angiosonographycorrelated with the pseudocystic appearance at CT. The ‘‘nodule(s) within a mass’’pattern of recurrence occurred in two patients with no difference observed between angiosonographyand CT. Earlydecreasing serum vascular endothelial growth factor levels were observed in the two cases with higher pretreatment levels. Conclusions: Imatinib could induce antiangiogenic and/or antivascular effects in GIST, and this effect could be easilymonitored with angiosonography.Angiosonographymight be a useful complement for monitoring the therapeutic effect of imatinib in these patients.

The use of imatinib in gastrointestinal stromal tumors (GIST) fluorodeoxyglucose positron emission tomography (PET) in represents the first effective development of a targeted therapy 80% to 90% of patients, before any measurable changes were for a solid neoplasm. Imatinib produces objective responses in seen on CT (3, 4). nearly 50% to 55% of patients (median time to response, 3-4 GIST metastases are typically intra-abdominal and hyper- months; range 1-12), and stable disease in 30% to 35% as vascular (5). The accuracy of ultrasound in the detection of measured with computerized tomography (CT) or magnetic intra-abdominal metastases from GIST is lower than CT or resonance by standardized criteria (Southwest Oncology Group magnetic resonance, but the introduction of contrast agents led criteria, and Response Evaluation Criteria in Solid Tumors; refs. to new possibilities for functional imaging studies. BR1 1–3). These results correlated closely with findings of response (Sonovue, Bracco, Milan, Italy) is a new blood pool ultrasound based on metabolic functional imaging with fluorine-18 second-generation contrast agent, which consists of stabilized microbubbles of a totally innocuous sulfur hexafluoride gas, which is of low solubility. It is isotonic to human plasma and Authors’ Affiliations: 1Istituto Oncologico Romagnolo, Department of Oncology devoid of antigenic potential, as it does not contain any and 2Laboratoryof Clinical Pharmacologyand Toxicology,Santa Maria delle Croci proteineous material (6). BR1 allows angiosonography through 3 Hospital,Ravenna;and Department of Imaging, Delta Hospital, Lagosanto, Ferrara, continuous real-time examination during different vascular Italy phases of contrast enhancement using low transmission power, Received 10/6/04; revised 5/25/05; accepted 6/3/05. Grant support: Istituto Oncologico Romagnolo, ForlI' , Italy. expressed as mechanical index. We evaluated the effect of The costs of publication of this article were defrayed in part by the payment of page angiosonography with BR1 to monitor response during charges. This article must therefore be herebymarked advertisement in accordance imatinib treatment (400 mg oral administration, once daily) with 18 U.S.C. Section 1734 solelyto indicate this fact. in patients with metastatic GIST. Note: Presented at the 16th European Organization for Research and Treatment of Cancer-National Cancer Institute-AACR Symposium on ‘‘Molecular Targets and Cancer Therapeutics’’, Geneva, Switzerland, September 28 to October1, 2004. Requests for reprints: Ugo De Giorgi, Istituto Toscano Tumori-Department Patients and Methods of Oncology, San Giuseppe Hospital, Via Paladini 40, I-50053 Empoli, Florence, Italy. Phone: 39-349-222-1235; Fax: 39-0571-702671; E-mail: ugo___degiorgi@ Patients. Between May 2002 and February 2004, 10 consecutive yahoo.com. patients (8 males and 2 females) with known advanced KIT+ GIST were F 2005 American Association for Cancer Research. investigated with angiosonography and CT. Median age was 66 years doi:10.1158/1078-0432.CCR-04-2046 (range, 35-85). A pathologic review in other centers was done in all

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Table 1. Patient characteristics before imatinib treatment

Patient no. Age (y) Sex Histology Primary site Primary treatment Sites of disease before imatinib 1 80 M KIT+ GIST stomach radical resection liver, peritoneum 2 73 M KIT+ GIST ileum radical resection liver, peritoneum 3 66 M KIT+ GIST colon palliative surgeryliver 4 46 F KIT+ GIST duodenum radical resection liver 5 63 F KIT+ GIST retroperitoneum radical resection retroperitoneum 6 66 M KIT+ GIST ileum radical resection liver, peritoneum 7 85 M KIT+ GIST stomach radical resection liver 8 35 M KIT+ GIST peritoneum/retroperitoneum radical resection liver 9 69 M KIT+ GIST stomach radical resection liver 10 53 M KIT+ GIST stomach no surgeryliver, peritoneum, stomach

cases. No patient was previously treated with imatinib. Patient written consent. In nine additional patients, in the follow-up after GIST characteristics before imatinib treatment are listed in Table 1. In complete resection, CT and angiosonography were done at the same addition, nine more patients were studied with both techniques in the time points every 3 to 6 months. follow-up after complete resection of GIST. Vascular endothelial growth factor. We monitored the serum levels Imatinib treatment. All patients were treated with imatinib at the of the major angiogenic growth factor, vascular endothelial growth starting dose of 400 mg/d. The imatinib dose was modified during the factor (VEGF), in all patients at baseline, at 1, 2, and 4 weeks, and then treatment in patients with severe toxicities. In these cases, the treatment every month until treatment failure. The serum levels of VEGF were was briefly interrupted until toxicity recovery and then was restarted determined by ELISA. The analyses were carried out according to the with the imatinib dose of 300 mg/d. In patients with progressive manufacturer’s recommendations (Human VEGF, Pierce Endogen, disease, the imatinib dose was increased to 800 mg/d, if possible, Rockford, IL). according to the tolerance and compliance of patients. In cases with minimal progressive disease with unresectable disease, continuing Results imatinib treatment at 400 mg/d was considered. In patients with massive progressive disease, the imatinib treatment was stopped. Overall, five patients had z10 liver metastases, four patients Imaging techniques. The ultrasound examinations were done by had <10 liver lesions. Liver metastases appeared hypervascu- means of a Sequoia digital ultrasound scanner (Acuson, Mountain larized before imatinib treatment. Instead, only five peritoneal View, CA) equipped with a wideband C5-2 MHz convex probe. Before metastases in four patients were detected and appeared less contrast agent injection, the scanning plane of the abdomen that vascularized than liver lesions. included the nodule(s) was determined. After the baseline ultrasound Angiosonography showed a reduction in tumor vasculariza- examination, all patients underwent angiosonography using BR1. tion of the liver metastases in all cases (Fig. 1). The tumor Nonlinear imaging was done starting with high mechanical index and then reducing to a continuous low acoustic power (mechanical index = perfusion appeared reduced in the central part of the liver 0.20) for each patient. Twelve milliliters of a 5 mg/mL solution of BR1 metastases. With a median follow-up of 18 months (range were administered as an i.v. bolus. The whole vascular phase was 3-33), a reduction in tumor vascularization was initially studied, consisting of the arterial phase (15-30 seconds after the observed in all patients with liver metastases and in the patient injection), the portal phase (30-60 seconds), and the sinusoidal phase with a retroperitoneal mass only. In four patients, angiosonog- (60-240 seconds). A second injection of BR1 was needed in some cases. raphy documented progressive disease after 12, 21, 24, and 27 Moreover, patients underwent multi-phase helical CT (Mx8000, months of imatinib treatment. Philips Medical Systems, Eindhoven, the Netherlands). Each patient CT showed an initial tumor response according to standard- received a bolus of 120 mL of low-osmolar iodinated contrast medium ized criteria in six patients (median time to response, 4 months; (Iomeron 400, Iomeprol, Bracco, Milan, Italy). range 1-9), whereas in the other four patients, stable disease PET scan was not regularly done. However, PET was done in cases was documented lasting 12, 21, 24, and 24+ months, with changes in tumor features at angiosonography and/or CT as in the case of progressive disease. PET scans were carried out using a PET respectively. In these four patients, achieving initial stable tomograph (Advance scanner, GE Medical System, Waukesha, WI). PET disease based on CT, the first angiosonography done at was carried out after i.v. injection of 370 MBq of fluorodeoxyglucose; 6 months, documented a reduction in tumor vascularization images were recorded after 60 to 90 minutes. of 80%, 60%, >90%, and 70%, respectively. The reduction of Study protocol. In patients with advanced GIST treated with tumor perfusion of the liver metastases reported at angioso- imatinib, CT was done at baseline, at 1, 2, 4, and 6 months, and then nography correlated with the pseudocystic appearance which every 3 months. Angiosonography was done before treatment, at can be seen on post-contrast CT following imatinib treatment 6 months, and then every 6 months in the first five cases, but at the (Fig. 2). In four cases, during imatinib treatment, CT showed same time points of CT in the next five. Two radiologists evaluated the progressive disease according to angiosonography. In two cases percentage of sonographic contrast uptake during different vascular with progressive disease after 21 and 24 months of treatment, phases at each tumor site and compared results obtained by angiosonography and CT. In a single case, the last one (Table 1, the imatinib dose was increased to 800 mg/d, but these patient 10), we did a strict evaluation with angiosonography at 1, 2, 4, two patients experienced further progressive disease after 3 and 6, and 8 weeks in order to define the first time point of reduction in 9 months, respectively. tumor vascularization during imatinib treatment. The study protocol Of the four patients with recurrent disease, two presented was approved by the Institutional Review Board and patients provided a ‘‘classical’’ progressive disease with both regrowth of

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Fig. 2. Angiosonographywith BR1and CTof the right lobe in a patient with liver metastases from GIST after 12 months of imatinib treatment showing correspondence between the reduction of tumor perfusion at angiosonography with pseudocystic appearance at CT. A, angiosonographyreveals a dishomogeneous lesion (1), whereas lesions 2 and 3 appear hypoechoic during the late arterial phase with evident reduction in vascularization; B, CTshows a lesion with a mixed appearance (1), whereas lesions 2 and 3 show a pseudocystic appearance.

Fig. 1. Angiosonographywith BR1of the right lobe of the liver in a patient with liver metastasis from GIST before and after 2 months of imatinib treatment. A, unenhanced sonographywith detection of one lesion with small central hypoechoic area and hypoechoic halo around metastasis (arrow); B, following BR1 administration, in the same scan of (A), liver metastasis appears isoechoic with respect to intenselybright normal parenchyma in the portal phase ( arrow); C, unenhanced sonographyafter 2 months of imatinib treatment shows one lesion with the same characteristics as unenhanced sonographybefore treatment (A; arrow); D, following BR1administration, in the same scan of (C) after 2 months of imatinib treatment, liver metastasis appears hypoechoic and completely surrounded byintenselybright normal parenchyma in the portal phase ( arrow).

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preexisting lesions and new sites of disease was revealed at both angiosonography and CT with an increase of fluorodeoxyglucose uptake on PET scan. In two other cases, a new pattern of progressive disease with ‘‘nodule(s) within a mass’’ only was revealed at both angiosonography and CT, but PET scan appeared negative (Fig. 3) or with a very small positivity (Fig. 4), at first recurrence. Serum VEGF levels behaved in a heterogeneous manner, but two cases with higher pretreatment serum VEGF levels showed early decreasing levels. Moreover, the classical pattern of recurrence-only was correspondent to increased serum VEGF levels (Fig. 5). In the single case receiving strict angiosonographic evaluation, a reduction in tumor vascularization was observed as early as 2 weeks, but standardized tumor response based on CT was reported only after 9 months. Liver subcentimetric metastases were better depicted with angiosonography. In the nine additional patients in follow-up after GIST complete resection, 21 CT and angiosonography were done at the same time points. No difference was observed in the detection of disease recurrence in two patients.

Discussion

The early experience with imatinib in GIST patients involved classical anatomic imaging methods for tumor response assessment. Validated response criteria (WHO, Southwest Oncology Group, and Response Evaluation Criteria in Solid Tumors) were used, but these methods are validated for other diseases with classical antiproliferative agents. Angiosonogra- phy with a second-generation contrast agent (BR1) is a simple, noninvasive, and reproducible imaging technique, which represents a new method of assessing changes in tumor vascularity. The results of this preliminary study show that angiosonography improved the display of tumor vascularity as well as the accuracy in identifying reduction in tumor vascularization. Because the number of the examined cases was relatively low, general predictions of therapeutic effects must be discussed with caution. It is very likely that an initial high vascularization and a strong reduction of tumor perfusion under treatment are correlated with the subsequent imatinib-related tumor size reduction. However, angiosonography showed an evident reduction in tumor vascularization in the cases achieving long-term stable disease based on CT according to standardized criteria. The reduction of tumor perfusion reported at angiosonography correlated with the pseudocystic appearance which can be seen on post-contrast CT during imatinib treatment. The

Fig. 3. Metastatic GIST in a patient with initial positive response to imatinib treatment showing the ‘‘nodule(s) within a mass’’pattern of progression during imatinib treatment (case 1). A, after 24 months of imatinib treatment, angiosonographyreveals two small contrast-enhanced nodules ( arrows)withina lesion hypoechoic during the late arterial phase with evident reduction in vascularization; B, CTobtained at the same time point of (A) shows two enhanced nodules (arrows) within the matrix of a low-attenuation mass; C, PETscan obtained at the same time point of (A)and(B) shows lack of fluorodeoxyglucose uptake in the treated lesion; D, after 33 months of imatinib treatment, despite the increase of the dose of imatinib to 800 mg/d, angiosonographyreveals the increase of the size of the two contrast-enhanced nodules (arrows); E, CTobtained at the same time point of (D) shows the increase of the size of the two enhanced nodules (arrows); F, PETscan obtained at the same time point of (D)and(E) shows a focal area of increased fluorodeoxyglucose uptake in the treated lesion (arrow).

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Fig. 5. Serum levels ofVEGF in 10 GIST patients with longitudinallytaken serum samples.Two patients achieved a classical progressive disease with both regrowth of preexisting lesions and new sites of disease (continuous black line): an increase of serum VEGF level was evident in both cases at progression.Two other patients showed a new pattern of progressive disease with a nodule within a mass only (intermittent black line): a clear increase of serum VEGF level was not evident. In the figure, when progressive disease was clinicallyevident is shown with a bold point. After first progression, in two cases, the dose of imatinib was increased to 800 mg/d with further progression with the same radiological pattern of the first. Arrow indicates the serum VEGF level spike coupled with classical progressive disease following a 3-week interruption of imatinib treatment because of severe asthenia in an 86-year-old patient. In two patients with higher pretreatment serum VEGF levels, an earlyreduction in serum VEGF levels was observed as earlyas1week: continuous (n = 1) and intermittent line (n =1).

effective overall response rate to imatinib treatment in GISTs might be higher than reported with standard anatomic imaging, according to standardized criteria. A new ‘‘nodule(s) within a mass’’ pattern of recurrence after response to imatinib has been recently described in the literature (7). In our series, two patients presented this pattern of recurrence, with no difference observed in the detection between angiosonography and CT. Importantly, a reduction in tumor vascularization observed before a reduction in tumor size, as assessed through standardized criteria, coupled with the observation that the perfusion is mainly reduced in the central part of the treated tumors is in line with recent studies monitoring antiangiogenic and antivascular therapy with functional imaging (8). A reduction in serum VEGF levels was observed as early as 1 week in the two cases with higher pretreatment serum VEGF levels (Fig. 5). Imatinib-mediated antiangiogenic and/or antivascular properties have been shown in experimental models and in vivo in chronic myelogenous leukemia, neuroblastoma, and prostate cancer (9–14). Imatinib could induce antiangiogenic and/or antivascular effects in GIST, possibly through an angiogenesis-dependent mechanism in- volving the downstream cascade of KIT in the tumor cells and/ or platelet-derived growth factor receptors in the endothelial tumor cells and/or an antimigratory and antiproliferative effect upon smooth muscle cells needed to surround and stabilize a

Fig. 4. Metastatic GIST in a patient with initial positive response to imatinib treatment showing the ‘‘nodule(s) within a mass’’pattern of progression during imatinib treatment (case 2). A, after 27 months of imatinib treatment, angiosonographyreveals a hypoechoic contrast-enhanced nodule ( arrow)within a mass; B, CTobtained at the same time point of (A) shows an enhanced nodule (arrow) within a mass; C, PET scan obtained at the same time point of (A)and (B) shows a small focal area of verylow increased fluorodeoxyglucose uptake in the treated lesion (arrow).

www.aacrjournals.org 6175 Clin Cancer Res 2005;11(17) September 1,2005 Downloaded from clincancerres.aacrjournals.org on October 2, 2021. © 2005 American Association for Cancer Research. Imaging, Diagnosis, Prognosis nascent tumor vessel (11, 15). This effect could be easily imatinib in GIST should be described through new criteria monitored with angiosonography. which should in part differ from those conventionally used for A translation research interaction between radiological cytotoxic drugs. findings and biological/clinical studies could be suggested. Large studies are warranted to compare angiosonography The close relation between clinical outcome and the findings with standard anatomic imaging (CT or magnetic resonance) on angiosonography indicates that such scanning might be a and metabolic functional imaging (fluorodeoxyglucose-PET) useful complement to standard anatomic imaging for moni- for monitoring the therapeutic effect of imatinib in patients toring the therapeutic effect of imatinib in patients with with metastatic GIST and the follow-up of patients after GIST metastatic GIST. Moreover, patterns of tumor response to complete resection.

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Ugo De Giorgi, Camillo Aliberti, Giorgio Benea, et al.

Clin Cancer Res 2005;11:6171-6176.

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