Heterogeneity of lymphocyte subsets in predicting immune checkpoint inhibitor treatment response in advanced lung cancer: an analysis across different pathological types, therapeutic drugs, and age groups.

Background: Immune checkpoint inhibitor (ICI) has become pivotal in the treatment of advanced lung cancer, yet the absence of reliable biomarkers for assessing treatment response poses a significant challenge. This study aims to explore the predictive value of various lymphocyte subsets in different lung cancer subtypes, thus potentially identifying novel biomarkers to improve ICI treatment stratification and outcomes.

Methods: We conducted a retrospective analysis of 146 stage III or IV lung cancer patients undergoing ICI treatment. The study focused on exploring the relationship between various lymphocyte subsets and the efficacy of ICIs, aiming to determine their predictive value for post-treatment outcomes.

Results: Subgroup analysis revealed a positive correlation (P=0.01) between lower CD3⁺CD8⁺ T lymphocyte levels and treatment response in squamous cell carcinoma patients. However, no significance was observed in lung adenocarcinoma patients. Additionally, the predictive ability of lymphocyte subsets for different immunotherapy drugs varies. In individuals receiving anti-programmed cell death ligand 1 (PD-L1) treatment, a lower CD3⁺CD8⁺ T lymphocyte levels is significantly associated with a positive treatment outcome (P=0.002), while there is no difference for programmed death 1 (PD-1) drugs. Among patients under 60, higher expression of CD3⁺CD4⁺ T lymphocytes (P=0.03) combined with lower CD3⁺CD8⁺ T lymphocyte levels (P=0.006) showed a statistically significant association with improved treatment response. However, in patients aged over 60, no discernible correlation was ascertained between lymphocyte subsets and therapeutic response. Through prognostic analysis, two distinct lymphocyte subsets were identified, both exerting considerable impact on progression-free survival subsequent to ICIs treatment: CD3⁺CD4⁺ T lymphocytes [hazard ratio (HR) =0.50, P=0.006] and CD3⁺CD8⁺ T lymphocytes (HR =1.78, P=0.02).

Conclusions: Our findings underscore the significant heterogeneity in the predictive value of distinct lymphocyte subsets for lung cancer patients undergoing ICI treatment. These findings are particularly salient when considering various pathological types, immunotherapeutic agents, and patient age groups.