Randomized Phase II Trial of Pazopanib Versus Placebo in Patients With Advanced Extrapancreatic Neuroendocrine Tumors...

Patients with advanced, well-differentiated extrapancreatic neuroendocrine tumors (epNETs) have limited systemic treatment options. Pazopanib, an oral multikinase inhibitor with activity against vascular endothelial growth factor receptor (VEGFR)-2 and -3, PDGFR-alpha and-beta, and c-Kit, was tested for efficacy in epNET.

We conducted a multicenter, randomized, double-blind, phase II study of pazopanib (800 mg once daily) versus placebo in low- to intermediate-grade epNET with radiologic progressive disease (PD) within 12 months of study entry. Previous somatostatin analog (SSA) was required for midgut tumors, and concurrent SSA was allowed. The primary end point was progression-free survival (PFS) by blinded independent central review. Unblinding and crossover were allowed if PD was confirmed by central review.

One hundred seventy-one patients (97 pazopanib and 74 placebo) were randomly assigned between September 2013 and October 2015. The majority had a midgut primary site (75%) and previous SSA treatment (93%). About half (49%) of the patients had functional tumors. The median follow-up was 61 months (95% CI, 60 to 63). Median PFS was 11.8 versus 7.6 months in pazopanib versus placebo, respectively (hazard ratio, 0.54 [95% CI, 0.37 to 0.79]; P < .001); 49 placebo patients crossed over to pazopanib. There was no significant difference in overall survival between the treatment arms. Rates of grade 3 or greater adverse events (regardless of attribution) were higher in pazopanib versus placebo (84% v 47%; P < .001), as were grade 5 death events (8% v 0%, P = .017).

Pazopanib compared with placebo significantly improves PFS in patients with progressive epNET, confirming that the VEGF signaling pathway is a valid target for therapy in epNET. However, after integrating the associated risks relative to the benefits, further development of pazopanib in this clinical context is not planned.