Activity of the EGFR-HER2 dual inhibitor afatinib in EGFR-mutant lung cancer patients with acquired resistance to reversible EGFR tyrosine kinase inhibitors.

BACKGROUND: The purpose of this study was to evaluate the efficacy of afatinib in EGFR-mutant metastatic NSCLC patients with acquired resistance to erlotinib or gefitinib.
MATERIALS AND METHODS: We retrospectively analyzed the outcome of patients with EGFR-mutant advanced NSCLC treated with afatinib after failure of chemotherapy and EGFR TKIs.
RESULTS: A total of 96 individuals were included in the study. According to EGFR status, most patients (n = 63; 65.6%) harbored a deletion in exon 19, and de novo T790M mutation was detected in 2 cases (T790M and exon 19). Twenty-four (25%) patients underwent repeated biopsy immediately before starting afatinib and secondary T790M was detected in 8 (33%) samples. Among the 86 patients evaluable for efficacy, response rate was 11.6%, with a median progression free-survival (PFS) and overall survival (OS) of 3.9 and 7.3 months, respectively. No significant difference in PFS and OS was observed according to type of last therapy received before afatinib, type of EGFR mutation or adherence to Jackman criteria, and patients benefiting from afatinib therapy had longer PFS and OS (P < .001). Outcome results for repeated biopsy patients were similar to the whole population, with no evidence of response in T790M-positive patients. All patients were evaluable for toxicity, and 81% experienced an AE of any grade, with grade 3 to 4 AEs, mainly diarrhea and skin toxicity, occurring in 19 (20%) patients.
CONCLUSION: Our results showed that afatinib has only modest efficacy in a real life population of EGFR mutant NSCLC patients with acquired resistance to erlotinib or gefitinib.