Longitudinal evaluation of EGFR mutation in plasma for non-small cell lung cancer patients with front-line chemotherapy

8099 Background: To investigate longitudinally epidermal growth factor receptor (EGFR) mutation status in the plasma of pre- and post-chemotherapy for patients with advanced non-small cell lung cancer. Methods: Total of 153 advanced lung cancer patients were included in this study. Plasma samples in pre- and post-chemotherapy ( 2 cycles after) were collected. The DNA concentration was determined by real-time PCR. The EGFR exon 19 and 21 were amplified by mutant-enriched PCR and detected by denaturing high performance liquid chromatograph (DHPLC). The associations between EGFR mutation, DNA level and chemotherapeutic response were analyzed. Results: Among the 153 pts, EGFR mutation were detected 41.2% (63/153) and 27.4% (42/153) in plasma of pre-and post-chemotherapy, respectively. The objective response rate was 31.4% (48/153) and the circulating DNA level trend to decrease after chemotherapy in PR group but increase in PD group (p=0.012). 25 and 73 cases showed consistent EGFR mutation and wild-type status in pre-treatment and post-treatment plasma, respectively. Among 38 patients with change from pre-treatment EGFR mutant-type to post-treatment wild-type status, 11 gained PR, 12 SD and 15 PD. While for 17 patients with change from pre-treatment EGFR wild-type to post-treatment mutant-type, PR, SD and PD were 8, 7 and 2, respectively. The change to mutant-type in post-treatment plasma were found to be significantly higher in PR and disease control than PD(P=0.047, P=0.042). Conclusions: The data indicated that chemotherapy could not only affect the DNA concentration but also change the EGFR mutation detection in plasma for pts with advanced NSCLC. Reason for EGFR mutation change related with response of chemotherapy deserves further study. No significant financial relationships to disclose.