Clinical significance of epidermal growth factor receptor gene mutations on treatment outcome after cytotoxic chemotherapy in Japanese patients with non-small cell lung cancer (NSCLC)

Abstract

7670 Background: The relationship between EGFR mutation status and clinical outcome has not fully been assessed in NSCLC patients receiving cytotoxic agents. The aim of this study was to clarify its association. We also examined if this association could be affected by the prior gefitinib treatment or not. Methods: Patients with advanced or postoperative recurrent NSCLC who received both cytotoxic chemotherapy and gefitinib monotherapy through their treatment course and whose tumors were assessable for EGFR mutation analysis were included in this study. EGFR mutation was determined in exons 19 and 21 by direct sequencing. Results: Sixty patients were included in the study, including 6 (10%) patients who received the first-line gefitinib monotherapy followed by cytotoxic chemotherapy in the second-line or later settings. Of the 54 (90%) patients, 22 also underwent subsequent cytotoxic chemotherapy after the relapse to gefitinib monotherapy. EGFR mutations were detected in 17 (28%) patients. In the first-line cytotoxic chemotherapy setting (n=54), EGFR mutations significantly affected progression-free survival (PFS) with 6-month PFS rates of 45.8 vs. 21.9% (p=0.05). This was also observed in the multivariate analysis (HR=0.42, p=0.04). EGFR mutation was also significantly correlated with overall survival (OS) in the multivariate analysis (HR=0.26, p <0.01). Contrary, in the 28 (47%) of 60 patients who received cytotoxic chemotherapy after gefitinib monotherapy, there were no differences in PFS stratified by EGFR mutation status. The sensitivity to gefitinib was, however, correlated with EGFR mutation status and its sensitivity was retained even in the second-line setting in patients with EGFR mutations. Conclusion: EGFR mutation was significantly associated with better PFS in the first-line cytotoxic chemotherapy regimens. However, its association was not observed in the cytotoxic regimens administered after the relapse to gefitinib monotherapy, while the sensitivity to gefitinib was associated with EGFR mutation even in the second-line or later setting. No significant financial relationships to disclose.