Relationship Between CD8+ T Cells and Prognosis of Esophageal Cancer Patients: A Systematic Review and Meta-analysis

Tumor infiltrating lymphocytes (TILs), especially CD8+ T cells, play an important role in the process of anti-tumor immune response and are significantly correlated with the prognosis of esophageal cancer (EC), but there are also inconsistent conclusions. This study aimed to comprehensively evaluate the relationship between invasive CD8+ T cells and the prognosis in patients with EC through meta-analysis, and to provide a basis for prognosis and immunotherapy for EC. Articles related to CD8+ T cells and EC prognosis in PubMed, Cochrane Library, Embase, and CNKI were searched. Cancer specific survival (CSS), overall survival (OS) and disease-free survival (DFS) served as endpoint events. Besides, Stata15.0 was adopted for meta-analysis, and hazard ratio (HR) and 95% confidence interval (95%CI) for calculation of combined effect sizes. Total 547 articles were retrieved and 27 articles were finally enrolled, including 3988 cases of EC patients. Meta-analysis showed that high CD8 expression levels in tumor tissues, especially those in cancer nests, were associated with longer OS (HR = 0.74, 95% CI 0.67–0.81) and DFS (HR = 0.90, 95% CI 0.85–0.95) in EC patients ( P < 0.05). CD8+ T cells play an important role in the prognosis of EC patients and are indispensable components for the immune score of EC. Graphical Abstract This study aims to comprehensively evaluate the relationship between invasive CD8+ T cells and the prognosis of patients with esophageal cancer (EC) through meta-analysis. The results show that CD8+ T cells are associated with the prognosis of EC and have important predictive value, especially the survival time of EC patients with high intratumoral CD8+ TIL infiltration level is longer.