Clinical and biomarker evaluations of sunitinib in patients (pts) with advanced well-differentiated grade 3 (G3) and poorly differentiated neuroendocrine neoplasms (PD-NEN).

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274 Background: Angiogenesis is extensively developed in well-differentiated pancreatic neuroendocrine tumors (PNET) where sunitinib was showed to prolong progression-free survival leading to FDA and EMA approval. However, clinical experience in pts with well-differentiated G3 & PD-NEN remains limited. Methods: This prospective phase II trial evaluate potential biomarkers correlating with sunitinib activity in pts with advanced well differentiated G3 or PD-NEN. Sunitinib was given at the dose of 37.5 mg/d as a continuous daily dosing until progression or unacceptable toxicity. Evaluation of activity was based on RECIST1.1. Safety was evaluated according to NCI-CTCAEv4. Pharmacokinetics (PK) of sunitinib and SU12662 (main active metabolite) were evaluated. Tumor biomarkers (PDGFR-b, VEGFR2, Carbonic Anhydrase 9, Ki67 and p-AKT) were evaluated in tumor tissues, quantified in tumor cells and stroma (vessels, fibroblasts) using immunohistochemistry and correlated with response by RECIST. Results: Among 31 pts (M/F: 18/13, median age 61), 13 pancreatic, 5 gastric, 5 rectal, 4 colonic, and 4 other G3 & PD-NEN were entered. 27 pts had previous treatment with chemotherapy (mainly platinum/VP16). Among 26 pts evaluable for safety and activity, 7 pts (23%, 95%CI: 6.9%-39.3%), including 3 pts classified as well-differentiated G3 neoplasms) experienced partial responses and tumor stabilizations (clinical benefit). Safety and PK exposure to sunitinib and SU12662 in those pts was consistent with that experienced in PNET. Among the above evaluated tumor biomarkers, only Ki67 correlated with sunitinib activity. The median Ki67 was 20% and 77.5% in pts with CB versus non-responders (p=.002), respectively. ROC curves showed correlations between lower Ki67 in tumors and sunitinib activity (OR:0.9; IC95%:0.831-0.9, p=.039). With a threshold value of Ki67 of 47%, sensitivity and specificity were 80%, the predictive positive value was 67% and the negative predictive value was 86%. Conclusions: In pts with well-differentiated G3 & PD-NEN, sunitinib showed evidence of activity that was more pronounced in pts with Ki67<47%. Clinical trial information: NCT01215578.