PDCD1 and esophageal squamous cell carcinoma: On the contrary, another study showed that in the first-line treatment of advanced esophageal squamous cell carcinoma, the curative effect of anti-PD-1 antibody combined with chemotherapy in people with low PD-L1 expression was still significantly better than that of chemotherapy alone [47], which added strong evidence in favor of the application of combined therapy in patients with low PD-L1 expression, and also demonstrated that the relationship between PD-1/PD-L1 expression level and the anti-PD-1 curative effect was not consistent.