Impact of Histology on Clinical Outcomes of Pembrolizumab Monotherapy in Patients With Advanced or Metastatic Urothelial Carcinoma in the Phase 3 KEYNOTE-045 and KEYNOTE-361 Trials

Abstract

Introduction: A post hoc analysis of efficacy and safety outcomes with pembrolizumab monotherapy was conducted in patients with advanced or metastatic urothelial carcinoma (UC) with pure transitional cell carcinoma (TCC) or mixed predominant TCC histology enrolled in the phase 3 KEYNOTE-045 and KEYNOTE-361 studies.

Methods: Adults with platinum-refractory advanced or metastatic UC who received pembrolizumab monotherapy in KEYNOTE-045 and adults with advanced or metastatic UC and no prior systemic chemotherapy who received pembrolizumab monotherapy in KEYNOTE-361 were analyzed separately. Pembrolizumab 200 mg was administered intravenously every 3 weeks for ≤2 years. Histology was assessed by investigator. End points included objective response rate (ORR), progression-free survival, and duration of response per RECIST v1.1 by central radiology assessment, as well as overall survival (OS) and safety.

Results: In KEYNOTE-045, 268 patients had known histology (pure TCC: 186; mixed predominant TCC: 82). At data cutoff (October 1, 2020), median follow up was 62.9 months (range, 59.0-70.9). For pure TCC, confirmed ORR was 21.0% (95% CI, 15.4-27.5); median OS was 9.7 months (95% CI, 7.5-11.8). For mixed predominant TCC, confirmed ORR was 24.4% (95% CI, 15.6-35.1); median OS was 11.6 months (95% CI, 7.4-16.4). In KEYNOTE-361, 307 patients had known histology (pure TCC: 280; mixed predominant TCC: 27). At data cutoff (April 29, 2020), median follow-up was 32.5 months (range, 22.0-42.3). For pure TCC, confirmed ORR was 29.3% (95% CI, 24.0-35.0); median OS was 14.8 months (95% CI, 11.8-17.9). For mixed predominant TCC, confirmed ORR was 40.7% (95% CI, 22.4-61.2); median OS was 16.2 months (95% CI, 5.5-NR). Grade 3-5 treatment-related adverse events occurred at similar rates for treated patients in both studies.

Conclusion: In this post hoc analysis, efficacy and safety outcomes with pembrolizumab monotherapy were generally consistent for patients with advanced or metastatic UC in KEYNOTE-045 and KEYNOTE-361 studies between histology subgroups.

Clinical trial registration: ClinicalTrials.gov, KEYNOTE-045 (NCT02256436) and KEYNOTE-361 (NCT02853305).