1259P - GEFITINIB for Non-Small Cell Lung Cancer (NSCLC) with Minor EGFR Mutations: A Retrospective Study from the North East Japan Study Group (NEJ)

Abstract

ABSTRACT Background In NSCLC, the sensitive mutations of epidermal growth factor receptor (EGFR), such as exon 19 deletion and L858R point mutation, are predictors of response to EGFR tyrosine kinase inhibitors (TKIs). However, it is still uncertain whether minor EGFR mutations are associated with sensitivity to EGFR-TKIs. Materials and methods Retrospective review of 221 EGFR mutated (exon 19 deletion, L858R, G719X and L861Q) patients who were treated with gefitinib in a NEJ002 study was performed. We identified 7 patients with G719X and 3 patients with L861Q. Results Among 10 patients harboring minor EGFR mutations (G719X or L861Q), 5 patients were treated with gefitinib as the 1st line treatment, and 5 patients were treated with carboplatin/paclitaxel as the 1st line chemotherapy, and then received gefitinib as the 2nd line treatment. Only 2 patients showed PR, 4 achieved SD, and 4 had PD with gefitinib treatment. The overall response rate was 20% and the disease control rate was 60%. The overall survival (OS) from enrollment was significantly shorter in patients with minor mutations (median OS, 12 months (95% CI, 5.8 - 30.5)) compared to patients with 19 deletion or L858R (median OS, 28 months (95% CI, 24.1 – 33.2), P = 0.0057). Tendency of longer progression free survival and OS were observed in minor EGFR mutation patients who received carboplatin/paclitaxel as the 1st line treatment (median PFS, 5.3 months (95% CI, 3.7 – 8.9) and median OS, 22.8 months (95% CI, 9.9 – 41.8)) compared to those who were treated with gefitinib as the 1st line treatment (median PFS, 2.2 months (95% CI, 0.5 – 10.6), P = 0.997 and median OS, 11.9 months (95% CI, 5.8 – 22.6), P = 0.1021). Conclusions Our results indicate that NSCLC patients with G719X or L861Q minor EGFR mutations are less responsive to gefitinib than those with 19 deletion or L858R. Disclosure All authors have declared no conflicts of interest.