PDCD1 and esophageal squamous cell carcinoma: Prior studies indicated that concurrent radiotherapy plus camrelizumab elevated the expression levels of activation molecules CD38 and HLA-DR on CD8+ T cells, thereby enhancing the cytotoxicity and activation of PD-1+CD8+ T cells, which correlated with improved prognosis in patients with esophageal squamous cell carcinoma (45), potentially elucidating our findings.