Maintenance Pembrolizumab After First-Line Chemotherapy Improves Survival in Urothelial Cancer

By DocWire News Editors - Last Updated: June 4, 2019

Platinum-based chemotherapy for first-line treatment of metastatic urothelial cancer is typically administered for a fixed duration followed by observation. Previous research indicates that pembrolizumab improves survival of metastatic urothelial cancer that has progressed following platinum-based chemotherapy. Researchers assessed the potential benefit of earlier pembrolizumab using a “switch maintenance” approach and found that this may “deepen responses achieved with first-line chemotherapy.” The results of the multi-institutional, randomized, placebo-controlled, double-blind, phase II study were presented at the 2019 ASCO Annual Meeting.

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Researchers enrolled patients with metastatic urothelial cancer who achieved at least stable disease (SD) after up to eight cycles of first-line platinum-based chemotherapy. Between December 2015 and November 2018, 107 patients were randomized 1:1 to receive pembrolizumab 200 mg intravenously every three weeks (n=55; median age = 68 years; range = 41-83 years) or placebo (n=52; median age = 65 years; range = 44-87 years) for up to 24 months. Patients receiving placebo could cross over to receive pembrolizumab. Patients were stratified based on pre-chemotherapy visceral metastases (yes vs. no) and response to first-line chemotherapy (complete response (CR)/partial response (PR) vs. SD).

Most patients in both cohorts received cisplatin-based first-line chemotherapy: 39 patients (71%) in the pembrolizumab cohort and 41 (79%) in the placebo cohort. Most patients in both groups achieved a CR or PR to previous first-line therapy: 40 patients (73%) in the pembrolizumab group and 36 (69%) in the placebo group.

Patients received a median of six cycles of placebo and eight cycles of pembrolizumab. When researchers excluded patients with a CR at baseline, the objective response rate was 12% (n=5/42) with placebo and 22% (n=10/46) with pembrolizumab.

Grade 3/4 treatment-related adverse events occurred in 48% of patients receiving placebo and 56% of patients receiving pembrolizumab. At a median follow-up of 14.7 months, 41 patients died and 26 patients in the placebo cohort crossed over to receive pembrolizumab.

Progression-free survival (PFS; primary endpoint) was significantly longer in patients receiving pembrolizumab versus placebo (P=0.038). The 18-month restricted mean PFS was 5.6 months with placebo and 8.2 months with pembrolizumab (P=0.023).

Reference

Galsky MD, Pal SK, Mortazavi A, et al. Randomized double-blind phase II study of maintenance pembrolizumab versus placebo after first-line chemotherapy in patients (pts) with metastatic urothelial cancer (mUC): HCRN GU14-182. Abstract #4504. Presented at the 2019 ASCO Annual Meeting, Chicago, IL, June 3, 2019.

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