Clinical predictive factors for mutations in epidermal growth factor receptor (EGFR) exon 19 and 21 in Japanese patients with lung cancer

Abstract

18131 Background: It has been reported that lung cancer with activating mutations of EGFR are highly sensitive to gefitinib or erlotinib. Furthermore, the incidence of EGFR mutations is significantly higher in adenocarcinoma, female, never-smoker, Japanese patients. However, it is difficult to take sufficient amount of biopsy specimen of lung cancer with advanced disease for mutation analyses in clinical practice. Therefore, in this study, clinical predictive factors for EGFR mutations in Japanese patients with lung cancer were clarified. Methods: EGFR exon 19 and 21 mutation status was determined in 284 tumor samples using direct sequencing, polymerase chain reaction. To identify clinical independent predictive factors for EGFR mutation, the logistic regression analysis was performed. Results: 131 tumors of them could be analyzed for mutations in EGFR exon 19 and 21. EGFR mutations were detected in 38 tumors (29%). Median age of patients with EGFR mutations was 62 years (rage 43–84); 19 male and 19 female; 18 stage I, 15 stage II, and 5 stage III disease. Cigarette- smoking history of patients with EGFR mutations included non-smoker in 20 patients, light smoker (< 10 pack-years smoker) in 4, and heavy smoker (> 10 pack-years smoker) in 14. Multivariate analyses showed that non-smoker or light smoker (p=0.007) and adenocarcinoma (p=0.044) were the significant predictive factors contributing to EGFR mutations. Gender, serum CEA level, and clinical stage were not associated with EGFR mutations. Seventy patients treated with gefitinib and 25 PR were observed, and the overall response rate was 36%. The response rate to gefitinib in patients with and without EGFR mutations were 76% and 7%, respectively. In addition, EGFR mutations were detected in 51% (19/37) of patients with adenocarcinoma and light smoker, and the response rate to gefitinib of them was 49% (18/37). Conclusions: In Japanese patients with lung cancer, non-smoker or light smoker and adenocarcinoma were significant predictive factors for mutations in EGFR exon 19 and 21. No significant financial relationships to disclose.