Pembrolizumab for advanced penile cancer: a case series from a phase II basket trial.

Background: Treatment options for unresectable, locally advanced or metastatic penile squamous cell carcinoma (SCC) are limited. Previous studies have shown that 40-62% of patients with penile SCC express PD-L1. We report three cases of locally advanced or metastatic penile SCC treated with pembrolizumab.

Case Presentations: Herein, we present three patients with recurrent, locally advanced or metastatic penile SCC who progressed on a platinum-based chemotherapy triplet and were treated with pembrolizumab, administered as part of a phase II clinical trial for rare tumors (NCT02721732). One patient with a microsatellite instability high (MSI-H) tumor experienced a durable partial response to pembrolizumab, underwent surgical consolidation, and remains disease-free 38.7 months later. Two patients experienced progressive disease within 3 months of beginning pembrolizumab. No one experienced a grade 3 or worse treatment-related adverse event.

Conclusion: In sum, single-agent pembrolizumab was well tolerated as salvage therapy in a small cohort of patients with unresectable, locally advanced or metastatic penile SCC. Pembrolizumab produced an objective response in an MSI-H tumor, yet it did not control disease in two patients with MSS penile SCC. Rationale combination therapies, including pembrolizumab, warrant further investigation.

Trial Registration: ClinicalTrials.gov identifier: NCT02721732 . Registered March 23, 2016.