PDCD1 and esophageal squamous cell carcinoma: There was no significant difference between the immunological parameters of patients with ESCC (n = 73) before CRT and age, sex, lesion location, N stage, and M stage (p > 0.05), while the lesion length and PD-1 expression in CD3+ and CD4+T cells was statistically significant (p < 0.05), and the GTV had a statistical difference with the ratio of CD4+/CD8+ and CD4+ T cells (p < 0.05).