PDCD1 and esophageal squamous cell carcinoma: PD-1/PD-L1 inhibitors in the first-line setting, alone or in combination with other antitumor therapies, are increasingly being demonstrated to exhibit favorable long-term survival in many types of advanced-stage cancer, including melanoma, lung cancer, esophageal squamous cell carcinoma (ESCC), gastric carcinoma (GC) and many others (Doroshow et al., 2021).