Phase II trial of pembrolizumab in patients with platinum refractory germ-cell tumors: a Hoosier Cancer Research Network Study GU14-206.

Background: Despite remarkable results with salvage standard-dose or high-dose chemotherapy ∼15% of patients with relapsed germ-cell tumors (GCT) are incurable. Immune checkpoint inhibitors have produced significant remission in multiple tumor types. We report the first study of immunotherapy in patients with GCT.

Patients and methods: Single arm phase II trial investigating pembrolizumab 200 mg i.v. Q3weeks until disease progression in patients with relapsed GCT and no curable options. Patients age ≥18 with GCT who progressed after first-line cisplatin-based chemotherapy and after at least one salvage regimen (high-dose or standard-dose chemotherapy) were eligible. Centrally assessed programmed death-ligand 1 (PD-L1) on tumor and infiltrating immune cells was scored. Primary end point was overall response rate using immune-related response criteria. Simon two-stage design with type I error 20% and power 80% was utilized.

Results: Twelve male patients were enrolled. Median age was 38 years. All patients had nonseminoma. Primary site was testis (11) or mediastinum (1). Median AFP 615 (range 1-32, 760) and hCG 4 (range 0.6-37, 096). Six patients had late relapse (>2 years). Median number of previous chemotherapy regimens was 3. Six patients received prior high-dose chemotherapy. Two patients had positive PD-L1 staining (H-score 90 and 170). Median number of pembrolizumab doses was 2 (range 1-8). There were six grade 3 adverse events. No immune-related adverse events were reported. No partial or complete responses were observed. Two patients achieved radiographic stable disease for 28 and 19 weeks, respectively; both had continued rising AFP level despite radiographic stability and had negative PD-L1 staining.

Conclusion: This is the first reported trial evaluating immune checkpoint inhibitors in GCT. Pembrolizumab is well tolerated but does not appear to have clinically meaningful single-agent activity in refractory GCT.

Clinical trial information: NCT02499952.