Background: Sunitinib is an oral, multitargeted receptor tyrosine kinase inhibitor with antiangiogenic activity. In a phase III, double-blind, placebo-controlled, randomized trial in patients with advanced, well-differentiated progressive pancreatic neuroendocrine tumors (NET), sunitinib 37.5 mg continuous daily dosing significantly improved investigator-assessed progression-free survival (PFS) compared with placebo (median, 11.4 months vs. 5.5 months; hazard ratio [HR] 0.418; 95% CI: 0.263, 0.662; P=0.0001). To evaluate the possibility that recognizable treatment- associated adverse events (AEs) might have impacted the efficacy results by unblinding the investigators, we conducted a retrospective blinded independent central review (BICR) of the tumor imaging scans. Methods: PFS was defined as the time from randomization to the first objective progression of disease or death due to any cause, whichever occurred first. Baseline and on-study CT/MRI scans were evaluated independently according to a two-reader, two-time point lock, followed by a sequential locked read, batch mode paradigm, by independent, third party radiologists. Reading radiologists were blinded to investigator tumor assessments and AEs; discrepancies were adjudicated by a similarly blinded and independent third radiologist. Results: Overall, 171 patients were randomized to treatment (sunitinib, n=86, placebo, n=85). Scans were collected retrospectively for 170 (99.4%) patients. Complete scan sets/time points were available for 160 patients (93.6%). Median PFS based on BICR of scans was 12.6 months for sunitinib and 5.8 months for placebo with an HR of 0.315 (95% CI: 0.181, 0.546; p=0.000015), consistent with the investigator- assessed PFS results. Conclusions: This BICR of tumor scans confirms the investigator-assessed, clinically meaningful PFS benefit of sunitinib in patients with pancreatic NET, and provides evidence against the presence of any systematic bias favoring sunitinib.