M2-polarized macrophages contribute to the decreased sensitivity of EGFR-TKIs treatment in patients with advanced lung adenocarcinoma

Previous study has revealed that tumor-associated macrophages (TAMs) correlate with response to epidermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) in advanced non-small cell lung cancer (NSCLC). In the present study, we further determined that M2-TAMs, but not M1-TAMs, are related to the treatment response to EGFR-TKIs in advanced NSCLC and may be an independent predictor of survival. Eighty-eight advanced lung adenocarcinoma patients treated with a second-line EGFR-TKI were involved in this study. M2-TAMs counts but not M1-TAMs were significantly higher in patients with progressive disease than in those without (P < 0.001). A trend also remained in patients with known EGFR status (n = 61) and those with mutant EGFR (n = 49). High M2-TAMs counts were shown to be significantly related to poor progression-free survival (PFS) and overall survival (OS) in all patients, or subsets of patients with known EGFR status or patients with EGFR mutation (all P < 0.05). Multivariate Cox analyses showed that high M2-TAMs counts and EGFR mutations were both independent factors associated with PFS and OS (P < 0.05). Overall, we revealed that M2- but not M1-TAMs are related to the response of EGFR-TKIs treatment irrespective of EGFR mutation and can independently predict survival in advanced lung adenocarcinoma treated with a second-line EGFR-TKI.