PDCD1 and esophageal squamous cell carcinoma: In a recent multicenter, double‐blind, randomized phase III ASTRUM‐007 trial, we reported that serplulimab (a monoclonal anti‐PD‐1 antibody) plus chemotherapy significantly improved PFS and OS compared with placebo plus chemotherapy in patients with previously untreated, locally advanced, or metastatic ESCC.13