Pembrolizumab alone or combined with chemotherapy versus chemotherapy as first-line therapy for advanced urothelial carcinoma (KEYNOTE-361): a randomised, open-label, phase 3 trial.

PD-1 and PD-L1 inhibitors are active in metastatic urothelial carcinoma, but positive randomised data supporting their use as a first-line treatment are lacking. In this study we assessed outcomes with first-line pembrolizumab alone or combined with chemotherapy versus chemotherapy for patients with previously untreated advanced urothelial carcinoma. KEYNOTE-361 is a randomised, open-label, phase 3 trial of patients aged at least 18 years, with untreated, locally advanced, unresectable, or metastatic urothelial carcinoma, with an Eastern Cooperative Oncology Group performance status of up to 2. Eligible patients were enrolled from 201 medical centres in 21 countries and randomly allocated (1:1:1) via an interactive voice-web response system to intravenous pembrolizumab 200 mg every 3 weeks for a maximum of 35 cycles plus intravenous chemotherapy (gemcitabine [1000 mg/m] on days 1 and 8 and investigator's choice of cisplatin [70 mg/m] or carboplatin [area under the curve 5] on day 1 of every 3-week cycle) for a maximum of six cycles, pembrolizumab alone, or chemotherapy alone, stratified by choice of platinum therapy and PD-L1 combined positive score (CPS). Neither patients nor investigators were masked to the treatment assignment or CPS. At protocol-specified final analysis, sequential hypothesis testing began with superiority of pembrolizumab plus chemotherapy versus chemotherapy alone in the total population (all patients randomly allocated to a treatment) for the dual primary endpoints of progression-free survival (p value boundary 0·0019), assessed by masked, independent central review, and overall survival (p value boundary 0·0142), followed by non-inferiority and superiority of overall survival for pembrolizumab versus chemotherapy in the patient population with CPS of at least 10 and in the total population (also a primary endpoint). Safety was assessed in the as-treated population (all patients who received at least one dose of study treatment). This study i