Twelve-month PFS estimates were 13.6% with pembrolizumab plus EP and 3.1% with placebo plus EP….Pembrolizumab plus EP significantly improved PFS compared with placebo plus EP as first-line therapy for patients with ES-SCLC. Pembrolizumab plus EP significantly improved PFS compared with placebo plus EP as first-line therapy for patients with ES-SCLC.