Abstract Background Afatinib has shown favorable response rates (RRs) and longer progression free survival (PFS) in lung cancer patients harboring EGFR mutations compared with standard platinum-based chemotherapy. However, serious adverse drug reactions (ADRs) limit the clinical application of afatinib. Methods We designed a retrospective study, enrolling all patients with metastatic lung adenocarcinoma who were diagnosed and treated with 30 or 40 mg daily afatinib as their initial treatment in three Kaohsiung Medical University-affiliated hospitals in Taiwan. Results A total of 179 patients were enrolled in the study, of which 102 (57%) and 77 (43%) received 30 mg and 40 mg afatinib daily as their initial treatment, respectively. The patients initially using 30 mg afatinib daily had a similar RR (75% vs. 83%, p = 0.1672), median PFS (14.5 vs. 14.8 months, log-rank p = 0.4649), and median OS (34.0 vs. 25.2 months, log-rank p = 0.5982) compared with those initially using 40 mg afatinib daily. Patients initially receiving 30 mg afatinib daily had fewer ADRs compared with those using 40 mg daily. The overall incidence of moderate and severe ADRs was significantly lower in patients receiving 30 mg afatinib daily compared with those using 40 mg daily (49% vs. 77%, p = 0.002); similar findings was observed in terms of severe ADRs (7% vs. 24%, p < 0.0001). Conclusion Patients receiving 30 mg afatinib daily as their initial treatment had similar RR, PFS, OS, but significantly fewer serious ADRs, as compared with those using 40 mg as their starting dose.
