The impact of epidermal growth factor receptor (EGFR) mutation in locally advanced non-small-cell lung cancer (NSCLC) remains controversial. This study was conducted to investigate the clinical outcomes and recurrence patterns after definitive chemoradiotherapy (CRT) in patients with unresectable stage III non-squamous-cell lung cancer according to EGFR mutation status. We retrospectively reviewed 604 patients with pathologically confirmed stage III NSCLC who were treated with definitive CRT

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... were examined for EGFR mutation at Samsung Medical Center, Korea, from January 2013 to December 2018. Among them, we identified 236 patients with stage III non-squamous-cell lung cancer who were treated with definitive CRT and were examined for EGFR mutation status. We analyzed the frequency of EGFR mutation, progression-free survival (PFS), overall survival (OS), objective response rate (ORR), and recurrence pattern. Among 236 patients, EGFR mutation was detected in 71 patients (30.1%) and the median follow-up duration was 41.7 months. There were no significant differences in PFS (9.9 vs. 10.9 months, p=0.236), and ORR to CRT (93.0% vs. 90.3%, p=0.623) according to EGFR mutation status. However, the EGFR mutant group showed significantly higher recurrence (88.7% vs. 75.2%, p=0.022), distant metastasis (76.1% vs. 61.2%, p=0.036) rates, especially brain (38.0% vs. 12.7%, p<0.001), and better median OS (59.2 vs 41.3 months, p=0.037) compared with patients without EGFR mutation. Patients with EGFR mutation-positive unresectable stage III non-squamous lung cancer exhibited higher recurrence and distant metastasis rates, especially brain metastasis.