Tumor-associated macrophages correlate with response to epidermal growth factor receptor-tyrosine kinase inhibitors in advanced non-small cell lung cancer

Our study investigated whether tumor-associated macrophages (TAMs) in advanced non-small cell lung cancer (NSCLC) are related to treatment response to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) and may be a predictor of survival. Of 206 advanced NSCLC patients treated (first-line) with an EGFR-TKI at the study hospital from 2006 to 2009, 107 with adequate specimens for assessing CD68 immunohistochemistry as a marker of TAMs were assessed. After EGFR-TKI treatment, response was observed in 55 (51%) patients, and the median follow-up period was 13.5 months. Most TAMs were located in the tumor stroma (>95%) and positively costained with the M2 marker CD163. TAM counts were significantly higher in patients with progressive disease than in those without (p <0.0001), a trend that remained in patients with known EGFR mutation status (n = 59) and those with wild-type EGFR (n = 20). High TAM counts, among other factors (e.g., wild-type EGFR), were significantly related to poor progression-free survival (PFS) and overall survival (OS) (all p <0.0001 for TAMs). Multivariate Cox analyses showed that high TAM counts and EGFR mutations were both independent factors associated with PFS [odds ratio (OR), 8.0; 95% confidence interval (CI), 2.87-22.4; p = 0.0001 and OR, 0.03; 95% CI, 0.003-0.31; p = 0.003, respectively] and OS (OR, 2.641; 95% CI, 1.08-6.5; p = 0.03 and OR, 0.14; 95% CI, 0.03-0.56; p = 0.006, respectively). TAMs are related to treatment response irrespective of EGFR mutation and can independently predict survival in advanced NSCLC treated with an EGFR-TKI.