Association of lymphocyte subsets with the efficacy and prognosis of PD‑1 inhibitor therapy in advanced gastric cancer: results from a monocentric retrospective study.

Purpose: This retrospective study aimed to investigate the changes in peripheral blood lymphocyte subsets before and after immunotherapy in patients with advanced gastric cancer and their relationship n with the therapeutic efficacy and clinical prognosis.

Methods: Peripheral blood lymphocyte subsets, including CD4 + T cells, CD8 + T cells, CD4+/CD8 + ratio, NK cells, Treg cells, and B cells, were collected from 195 patients with advanced gastric cancer who were admitted to the First Hospital of Shanxi Medical University with immunotherapy from January 2020 to October 2021, at the time of diagnosis of advanced gastric cancer, before immunotherapy and after 3 cycles of immunotherapy. T-tests were used to examine the factors influencing the patients' peripheral blood lymphocyte subsets and the changes after immunotherapy. To examine the relationship between lymphocyte subsets and treatment outcomes, ROC curves were plotted using a logistic regression. Kaplan-Meier curve was drawn, and the Log Rank test was carried out to compare the differences in PFS between the different groups. Cox proportional hazards regression model was used to analyze the factors affecting PFS after calibration of other variables.

Results: The proportion of peripheral blood lymphocyte subsets in patients with advanced gastric cancer was affected by age and PD-L1 level. Compared to the baseline, the treatment effective group had higher proportions of CD4 + T cells, a higher CD4+/CD8 + ratio, NK cells and Treg cells, and lower proportions of CD8 + T cells and B cells in the peripheral blood after three cycles of immunotherapy. In the treatment-naive group, there were no significant differences in the lymphocyte subsets. With cut-off values of 30.60% and 18.00%, baseline CD4 + T cell and NK cell ratios were independent predictors of immunotherapy efficacy and PFS. Treg cell ratio, gender, PD-L1 levels, and MMR status all predicted PFS independently.

Conclusion: The proportion of peripheral blood lymphocyte subsets was modified in patients who responded to PD-1 inhibitors. Different lymphocyte subpopulation levels can be used as biomarkers to predict immunotherapy efficacy and clinical prognosis in patients with advanced gastric cancer.