Multicenter phase 3 trial of adjuvant pembrolizumab versus observation in muscle-invasive urothelial carcinoma

Muscle –invasive utrothelial carcinoma (MIUC) is an aggressive disease with high rates of relapse after radical surgery. The multicenter phase 3 AMBASSADOR trial in the United States evaluated adjuvant pembrolizumab for high-risk MIUC. Patients after radical surgery were randomized to pembrolizumab 200 mg every three weeks for one year (n=354) or observation. Coprimary endpoints were disease-free survival (DFS) and overall survival. At data cutoff the median follow-up for DFS was 44.8 months. The median DFS was 29.6 months in the pembrolizumab group and 14.2 months in the observation group (HR 0.73; p=0.003). Grad 3 or higher adverse events (regardless of attibution) occurred in 50.7% of patients in the pembrolizumab group and in 31.6% of the patients in the observation group. The authors conclude that among patients with high-risk MIUC after radical surgery, DFS was significantly longer with adjuvant pembrolizumab than with observation.