Subgroup analyses indicated higher efficacies of pembrolizumab for patients with esophageal squamous cell carcinoma (ESCC) than those for patients with adenocarcinoma, and the Food and Drug Administration (FDA) approved pembrolizumab for patients with metastatic ESCC whose tumors express PD-L1 CPS ≥10 after ≥1 prior line of systemic therapy. Here, CD274 is linked to esophageal squamous cell carcinoma.