Peripheral Blood Lymphocyte Subpopulations as Predictive Biomarkers for First-line PD-1 Inhibitors Efficacy in ESCC

Purpose: ： This study aimed to analyze the correlation between peripheral blood lymphocyte subpopulations and the efficacy of ICIs treatment in esophageal squamous cell carcinoma patients. Methods: ： We conducted a retrospective analysis of medical records from ESCC patients diagnosed between January 2020 and October 2023 at Jiangsu Provincial People's Hospital. The median was used as the cut-off value for the lymphocyte subpopulation. All variables were included in univariate Cox regression analysis, and only those reaching a significance level of P < 0.05 were incorporated into multivariate Cox regression analysis. Kaplan-Meier curves were applied to assess PFS. Results: ： Multivariate Cox regression analysis indicated that peripheral blood CD16+CD56+ lymphocytes (HR 0.359, 95% CI 0.174-0.739; p=0.005) and the presence of visceral metastasis (HR 3.056, 95% CI 1.334-7.005; p=0.008) are independent predictive factors for esophageal cancer patients. Kaplan-Meier survival curves showed that patients with higher CD16+CD56+ lymphocyte levels (CD16+CD56+-high versus CD16+CD56+-low, 18.9 versus 10.3 months, P=0.024) and those with a higher CD4+/CD8+ ratio (CD4+/CD8+-high versus CD4+/CD8+-low, 15.8 versus 9.6 months, P=0.038) had longer progression-free survival (PFS). Conversely, patients with a history of prior chemotherapy (Yes versus No, 5.8 versus 12.7, p=0.013), a history of prior surgery (Yes versus No, 5.5 versus 12.7, p=0.04), and those with visceral metastasis (Yes versus No, 5.8 versus 12.7, p=0.013) had shorter PFS. Conclusion: ： Our study suggests that baseline peripheral blood CD16+CD56+ lymphocytes and visceral metastasis are independent predictive biomarkers for first-line PD-1 inhibitors in esophageal squamous cell carcinoma patients.