Study of Pembrolizumab With or Without Platinum-based Combination Chemotherapy Versus Chemotherapy Alone in Urothelial Carcinoma (MK-3475-361/KEYNOTE-361)

The purpose of this study is to determine the efficacy and safety of pembrolizumab (pembro, MK-3475) with or without chemotherapy versus chemotherapy alone in participants with advanced or metastatic urothelial carcinoma (bladder cancer). The primary hypotheses are that pembrolizumab plus chemotherapy is superior to chemotherapy alone with respect to Progression-free Survival (PFS) and Overall Survival (OS) in all participants, and that pembrolizumab alone is superior to chemotherapy alone with respect to OS in all participants and in participants with programmed cell death ligand 1 (PD-L1) positive tumors (Combined Positive Score \[CPS\] ≥10%).