Associations of immune checkpoint inhibitor therapy efficacy with clinical parameters and tumor‑infiltrating CD68‑positive cell counts in patients with EGFR‑mutant non‑small cell lung cancer

Immune checkpoint inhibitor (ICI) therapy has been less effective in patients with non-small cell lung cancer (NSCLC) harboring epidermal growth factor receptor (EGFR) mutations than in patients with EGFR wild-type NSCLC. This retrospective study was conducted to investigate the associations of clinical parameters with the efficacy of ICI therapy in patients with EGFR-mutant NSCLC. Clinical information was retrieved from the medical charts, and immunohistochemical analysis was performed in some cases to determine the tumor-infiltrating CD68-positive cell count. Data from 46 patients were included in the analysis. The median (95% confidence interval) progression-free survival and overall survival from the initiation of ICI therapy was 1.4 months (1.0-1.7 months) and 6.4 months (3.9-19.0 months), respectively. Analysis using a Cox proportional hazards model revealed that tumor programmed death-ligand 1 expression was associated with the overall survival of patients with EGFR-mutant NSCLC after ICI treatment. The tumor-infiltrating CD68-positive cell count was evaluated in 11 patients. Comparison using the log-rank test revealed that the progression-free survival time after ICI treatment was longer in the patients with lower tumor-infiltrating CD68-positive cell counts than those with higher tumor-infiltrating CD68-positive cell counts. The present analysis demonstrated that PD-L1 expression and the tumor-infiltrating CD68-positive cell count may be associated with the efficacy of ICI therapy in patients with NSCLC harboring EGFR mutations.