BackgroundThis study aimed to investigate the factors associated with prolonged progression‐free survival (PFS) (>36 months) of advanced non‐small cell lung cancer (NSCLC) patients harboring epidermal growth factor receptor (EGFR) mutations treated with first‐line afatinib.MethodsWe performed a retrospective analysis of data of patients with advanced EGFR‐mutated NSCLC receiving first‐line afatinib at two tertiary care referral centers, Linkou and Kaohsiung Chang Gung Memorial Hospital, in Taiwan between June 2014 and April 2022.ResultsThe data of 546 treatment‐naïve EGFR‐mutated advanced NSCLC patients were analyzed. Median PFS and overall survival were 14.5 months and 27.2 months, respectively. The PFS of 462 patients (84.6%) was less than 36 months and of 84 patients (15.4%) was more than 36 months. The PFS > 36 months group had a significantly higher percentage of patients with uncommon mutations (p = 0.002). The PFS ≤36 months group had significantly higher incidences of bone, liver, and adrenal metastases (all p < 0.05) and a higher rate of multiple distant metastases. Multivariate logistic regression analysis showed that liver metastasis was negatively and independently associated with prolonged PFS (adjusted odds ratio = 0.246 [95% CI: 0.067–0.908], p = 0.035). The median overall survival of the PFS >36 months group was 46.0 months and that of the PFS ≤36 months group was 22.9 months (log‐rank test, p < 0.001).ConclusionsWe found that EGFR‐mutated NSCLC patients receiving first‐line afatinib were prone to shorter PFS if they had distant organ metastasis, especially liver metastasis.