KEYNOTE-590 was the first phase III trial to demonstrate the efficacy of programmed cell death protein-1 (PD-1) inhibitor-based immunochemotherapy as a first-line treatment for advanced or metastatic esophageal squamous cell carcinoma (ESCC) and esophageal adenocarcinoma (EAC). Here, PDCD1 is linked to esophageal squamous cell carcinoma.