Activity of Afatinib in Heavily Pretreated Patients With ERBB2 Mutation–Positive Advanced NSCLC

Introduction: Approximately 1% to 4% of NSCLC tumors harbor erb-b2 receptor tyrosine kinase 2 (ERBB2) mutation; there is no approved targeted treatment for this subgroup. Methods: Patients with stage IV NSCLC that progressed after clinical benefit on erlotinib/gefitinib and/or had activating EGFR or ERBB2 mutations, had exhausted other treatments, and were ineligible for afatinib trials were enrolled in a named patient use program, receiving afatinib 30 to 50 mg/d on a compassionate basis within routine clinical practice. Efficacy and safety were retrospectively assessed in the subgroup with ERBB2 mutation-positive NSCLC. Results: Twenty-eight heavily pretreated patients in the named patient use program had a documented ERBB2 mutation by local testing. Median time-to-treatment failure (TTF; time from treatment initiation to discontinuation for any reason) was 2.9 months; eight patients (29%) had TTF greater than 1 year. Objective response rate was 19% (3 of 16 patients with response data achieved partial response) and disease control rate (DCR) was 69% (11 of 16). Among 12 patients for whom type of ERBB2 mutation was specified, 10 had a p.A775_G776insYVMA insertion in exon 20, four of whom (40%) remained on afatinib for more than 1 year. This subgroup had median TTF of 9.6 months, objective response rate of 33% (two of six), and disease control rate of 100% (six of six). Conclusions: This analysis of patients treated in clinical practice provides further evidence of the activity of afatinib in ERBB2 mutation-positive NSCLC, and suggests that identification of specific subgroups with certain mutations, such as p.A775_G776ins/YVMA insertion in exon 20, could help optimize outcomes with ErbB2-targeted treatment.