Peripheral blood lymphocyte subpopulations as predictive biomarkers for first-line programmed death 1 inhibitors efficacy in esophageal squamous cell carcinoma: A retrospective study

Esophageal cancer (EC) poses a significant global health burden, necessitating effective treatment strategies. Immune checkpoint inhibitors have emerged as a promising therapeutic option for EC, but the identification of predictive biomarkers remains crucial for optimizing patient outcomes. We conducted a retrospective analysis of medical records from advanced esophageal squamous cell carcinoma patients treated with first-line programmed death 1 inhibitors. Peripheral blood lymphocyte subpopulations were evaluated using flow cytometry, while hematological tests provided data on neutrophil, lymphocyte, and monocyte counts. Cox regression and logistic regression analyses were employed to explore the association between lymphocyte subpopulations, baseline characteristics, and progression-free survival (PFS). Among the 100 initially included patients, 70 met eligibility criteria. Multivariate Cox regression analysis revealed a significant association between high CD16+CD56+ lymphocyte proportions and longer PFS, independent of other clinical variables. Similarly, a high CD4+/CD8+ ratio was correlated with prolonged PFS. Kaplan-Meier survival curves supported these findings. Logistic regression analysis indicated no significant differences in the CD4+/CD8+ ratio and CD16+CD56+ lymphocytes concerning baseline characteristics, suggesting their potential as independent prognostic markers. Our study highlights the predictive value of peripheral blood CD16+CD56+ lymphocytes and the CD4+/CD8+ ratio for the efficacy of programmed death 1 inhibitors in advanced esophageal squamous cell carcinoma patients. These findings underscore the importance of peripheral blood biomarkers in guiding personalized immunotherapy strategies and improving outcomes for EC patients.