PDCD1 and esophageal squamous cell carcinoma: CheckMate 648, a global, phase 3 trial, showed that first-line nivolumab (anti-PD-1 antibody) plus ipilimumab (NIVO + IPI) or nivolumab plus chemotherapy (NIVO + Chemo) significantly increased survival in advanced esophageal squamous cell carcinoma (ESCC) without new safety signals versus chemotherapy alone (Chemo).