Background: Afatinib is a second-generation epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor (TKI). Compared to cytotoxic chemotherapy, afatinib has been shown to have better efficacy in the treatment of non-small cell lung cancer harboring EGFR mutations. However, 40 mg daily as the initial dose is often accompanied by serious adverse drug reactions (ADRs) and 28 to 53.3% of patients required a dose reduction. No previous study has compared the clinical efficacy and ADRs of different initial doses (40 mg vs. 30 mg daily) of afatinib in lung cancer treatment.
Methods: Patients with stage IV lung adenocarcinoma diagnosed and treated in two Kaohsiung Medical University-affiliated hospitals in Taiwan between May 2014 and August 2016 were identified and followed until December 2016. Demographic characteristics, responses, progression-free survival (PFS), overall survival (OS), and ADRs were recorded.
Result: A total of 48 patients with stage IV lung adenocarcinoma harboring susceptible EGFR mutations who received afatinib as their first-line therapy were enrolled. Patients using 30 mg daily as the initial dose tended to be older and female and have a smaller body size. The patients using 30 mg of afatinib daily as their initial dose had a similar response rate to those receiving 40 mg daily (76% vs. 95%, p = 0.0862) and the same disease control rate (100% vs. 100%, p = 0.1486). The PFS was similar between the patients receiving 30 mg or 40 mg of afatinib daily (median PFS: 469 vs. 443 days, log-rank p = 0.8418). Patients receiving 30 mg daily had a significantly lower incidence of diarrhea than those using 40 mg daily (41% vs. 100%, p < 0.0001).
Conclusion: An initial afatinib dose of 30 mg daily had similar response and progression-free survival rates as an initial dose of 40 mg daily, but resulted in fewer serious ADRs in this study.
Keywords: Adenocarcinoma; Adverse drug reaction; Afatinib; Epidermal growth factor receptor; Lung cancer; Tyrosine kinase inhibitor;diarrhea.