Web of Science, PubMed, Embase, and Cochrane Library databases were searched using search terms: “camrelizumab or nivolumab or pembrolizumab or serplulimab or sintilimab or toripalimab or PD-1 or PD-L1”, “chemotherapy”, “esophageal squamous cell cancer or esophageal cancer or esophageal carcinoma” and “randomized clinical trial or randomized controlled trial”. The gene discussed is CD274; the disease is esophageal squamous cell carcinoma.