Objective To observe the pre-radiotherapy immunological state in patients with esophageal carcinoma, and to explore its association with the clinical pathological characters and prognosis. MethodsTotally 91 patients with pathologically confirmed esophageal cancer received radiotherapy. The proportions of T-lymphocyte subsets and natural killer (NK) cells in the peripheral blood were detected by the flow cytometry before radiotherapy; healthy population was taken as control. The correlation of immunological stress state and clinical pathological parameters were further evaluated in the patients. Univariate analysis (Kaplan-Meier) and multivariable analysis (Cox proportional hazards regression analysis) were used for survival analysis.Results The proportions of CD3+CD4+ (Th) T cells, CD8+CD28+ T cells and NK cells in pre-radiotherapy esophageal carcinoma patients were significantly lower than those in the healthy population (P<0.05). We also found that the proportion of CD3+CD8+ (Ts) T-lymphocytes was positively correlated with lymph node metastasis (P<0.05) and the proportion of NK cells was positively correlated with TNM stage (P<0.05). Univariate analysis showed that the patients with high proportions of Th or CD8+CD28+ T cells had a better survival (P<0.05). The multivariate analysis revealed that the proportion of Th cells before radiotherapy was an independent prognostic factor for patients with esophageal carcinoma. Conclusion The pre-radiotherapy proportion of Th cells in the peripheral blood is an independent prognostic factor for patients with esophageal carcinoma.