Relationship between Epidermal Growth Factor Receptor Mutations and Adverse Events in Non-Small Cell Lung Cancer Patients treated with Afatinib

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors such as afatinib are used for non-small cell lung cancer (NSCLC) and show varying efficacy depending on EGFR gene mutation. Few studies have examined the relationship between EGFR gene mutations and the adverse events of afatinib in NSCLC. This retrospective study included 32 Japanese patients with NSCLC with EGFR gene mutation who were treated with afatinib between May 2014 and August 2018 at Kagawa University Hospital. Among the 32 Japanese patients with NSCLC treated with afatinib, 19 patients were positive for exon 19 deletion mutation (Del 19) and 13 patients were negative for Del 19. The incidence of grade ≥ 2 skin rash was slightly higher in patients positive for Del 19 (42.1% vs. 7.7%, P = 0.050). No significant differences were detected in other adverse events between the two patient groups. Patients positive for Del 19 also showed significantly longer median progression-free survival (288 vs. 84 days, P = 0.049). Our study indicates a higher incidence of skin rash associated with afatinib treatment in Japanese patients with NSCLC positive for Del 19 compared with patients without Del 19. The Del 19 positive patient group also showed better progression-free survival.