Prospective analysis of the epidermal growth factor receptor gene mutations in non-small cell lung cancer in Japan

7077 Background: Previous clinical trials have revealed that gefitinib is more likely to be effective in non-small cell lung cancer (NSCLC) with activating somatic mutations of epidermal growth factor receptor (EGFR). Most of those reports evaluated NSCLC patients who had post-operative recurrence and then received gefitinib retrospectively using their surgical specimens. However, many NSCLC patients are inoperable at diagnosis. Thus we conducted this study to examine EGFR mutation status by diagnostic tumor samples before gefitinib treatment and investigate the correlation between EGFR mutation and the efficacy of gefitinib. Methods: We prospectively evaluated various tumor samples obtained from NSCLC patients who had never received gefitinib for EGFR mutations in exon 18–23. For patients treated with gefitinib after the examination of EGFR mutations, the response to gefitinib was also evaluated. Results: From June 2004 to November 2005, 91 patients with advanced or post-operative recurrent NSCLC enrolled onto this study and 104 tumor samples were obtained from transbronchial biopsies, effusions, as well as surgical specimens. Thirty-two mutations including deletions in exon 19 in 23 patients and L858R in 9 patients were detected among those 91 patients; 30 in 81 adenocaricinoma, 1 in 2 adenosquamous cell carcinoma, and 1 in 5 large cell carcinoma. The mutations were found more frequently in female (51.9%) than male (12.8%), in never smoker (52.0%) than smoker (14.6%). Response rate of gefitinib in patients with EGFR mutations was 65.0% (13 of 20) compared to 37.5% (3 of 8) in patients without mutations. Among 7 patients with EGFR mutations who were examined multiple tumor samples, 3 had the discrepancy of EGFR gene status between different samples obtained at different time points, suggesting genetic heterogeneity of their tumors. The EGFR status of the most recent samples is likely to be correlated to the response to gefitinib. Conclusions: The EGFR mutation analysis was possible not only from surgical specimens but also from daily available diagnostic samples. For patients with EGFR mutations, gefitinib could achieve a promising high response rate. We propose to examine the most recent tumor samples to predict the sensitivity to gefitinib reliably. No significant financial relationships to disclose.