Abstract / Summary
Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have significantly improved outcomes in patients with EGFR-mutant non-small cell lung cancer (NSCLC), yet treatment responses vary. Evidence increasingly suggests that the tumor immune microenvironment may affect EGFR-TKI efficacy. This study investigated the association between intratumoral CD8 + T-cell infiltration and clinical outcomes in patients receiving EGFR-TKI therapy. This retrospective study included 84 patients with advanced EGFR-mutant NSCLC treated with first-, second-, or third-generation EGFR-TKIs. CD8 + T-cell infiltration was assessed by immunohistochemistry and classified as low (≤ 5%) or high (> 5%). Progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and disease control rate (DCR) were compared between groups. Survival was estimated using the Kaplan–Meier method and analyzed with the log-rank test. Prognostic factors were assessed using Cox proportional hazards models. Patients with low CD8 + T-cell expression had a higher DCR (100% vs. 86.5%) and longer median PFS (12.0 vs. 6.0 months; p < 0.001) than those with high expression. They also had a lower risk of progression (hazard ratio [HR] = 0.50, 95% confidence interval [CI] 0.30–0.90). Similar trends were observed in exploratory subgroup analyses by EGFR-TKI generation. In multivariate analysis, CD8 + T-cell expression remained independently associated with PFS. Median OS was not reached in either group at data cutoff. Low intratumoral CD8 + T-cell expression was associated with better disease control and longer PFS in EGFR-mutant NSCLC treated with EGFR-TKIs. CD8 + T-cell infiltration may serve as a prognostic biomarker, although prospective validation and further characterization of CD8 + T-cell functional states are needed before clinical application.