Background: Sunitinib was approved by the FDA in 2011 for treatment of progressive, well-differentiated, advanced pancreatic neuroendocrine tumors (pNETs) based on a pivotal phase III study (NCT00428597) that showed a significant increase in progression-free survival (PFS) over placebo following early study termination. Subsequently, the FDA requested a post-approval study to support these findings. Methods: In this open-label, phase IV clinical trial (NCT01525550), patients with progressive, well-differentiated, unresectable advanced/metastatic pNETs received continuous sunitinib 37.5 mg once daily. Eligibility criteria were similar to the phase III study. Primary endpoint was investigator-assessed PFS per RECIST 1.0. This study is ongoing. Results: Sixty one treatment-naïve and 45 previously treated patients with progressive pNETs were treated with sunitinib: mean age, 54.6 years; males, 59.4%; white, 63.2%; ECOG PS 0, 65.1% or PS 1, 34.0%; and prior somatostatin analog, 48.1% (treatment-naïve, 39.3%; previously treated, 60.0%). At the data cutoff date, 82 (77%) patients discontinued treatment, mainly due to disease progression (46%). Median duration of treatment was ~11.9 months. Investigator-assessed median PFS (mPFS) was 13.2 months (95% CI, 10.9–16.7) in the overall population, with comparable mPFS in treatment-naïve and previously treated patients (13.2 vs 13.0 months). mPFS per independent radiologic review was 11.1 months (95% CI, 7.4–16.6). Objective response rate (ORR) per RECIST was 24.5%: 21.3% in treatment-naïve and 28.9% in previously treated patients. Median overall survival, although not yet mature, was 37.8 months. Treatment-emergent, all-causality adverse events (AEs) reported by ≥ 20% of all patients included neutropenia, diarrhea, leukopenia, fatigue, hand–foot syndrome, hypertension, abdominal pain, dysgeusia, and nausea. Most common grade 3/4 AEs were neutropenia (22%) and diarrhea (9%). Conclusions: The mPFS of 13.2 months and ORR of 24.5% observed in this study support the outcomes of the pivotal phase III study of sunitinib in pNETs and confirm its activity in this setting. AEs were consistent with known safety profile of sunitinib. Clinical trial information: NCT01525550