Development of a skin rash within the first week and the therapeutic effect in afatinib monotherapy for EGFR-mutant non-small cell lung cancer (NSCLC): Okayama lung cancer study group experience

Background Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are now key agents in treating EGFR-mutant non-small cell lung cancer (NSCLC). The efficacy of gefitinib or erlotinib monotherapy can be predicted by the development of a skin rash. However, it has not been fully evaluated if this is the case with afatinib monotherapy. Methods We retrospectively studied 49 consecutive patients with EGFR-mutant NSCLC who received afatinib therapy between 2009 and 2015. The relationship of several toxicities with tumor response was examined. Results Grade 2, or more severe, common adverse events (AEs) included skin rash in 17 patients (35%), diarrhea in 19 (39%) and mucositis in 15 (31%). Of these, the number of patients who developed ≥Grade 2 AEs during the first week after the initiation of afatinib therapy was: five patients had skin rash (10%), 12 patients had diarrhea (25%) and four patients had mucositis (8%). As for an objective response, 21 (43%) of the 49 had a partial response. Associating the AEs with the antitumor effect, those who had a ≥Grade 2 skin rash within the first week tended to have a greater tumor response compared with those without a rash (80 vs. 39%; p = 0.077). Conclusion Our small study demonstrated that the early development of a skin rash might be associated with the response to afatinib monotherapy.