Our study confirmed that PD-L1 expression status could certainly be a biomarker for selecting more suitable patients to receive PD-1 blockade therapy, which was in accordance with the Food and Drug Administration’s approval of second-line pembrolizumab monotherapy for recurrent, locally advanced or metastatic ESCC patients expressing PD-L1 in the United States. This evidence concerns the gene PDCD1 and esophageal squamous cell carcinoma.