Effect of EGFR gene polymorphism on efficacy of chemotherapy combined with targeted therapy for non-small cell lung cancer in Chinese patients.

EGFR-TKI had become the first-line treatment of metastatic NSCLC and widely used in clinical. It was reported that there was difference in response rate between NSCLC patients with or without EGFR mutation. However, there was no relevant studies about the difference in clinical response among patients with different kinds of EGFR mutation. In this study, we recruited 464 patients with NSCLC between March 2014 and March 2015. Circulating tumor DNA (ctDNA) was isolated from plasma and identified EGFR gene mutations. Demographic characteristics, pathological data, safety and three-year survival were compared in patients with different EGFR gene mutations. The primary objective was progression-free survival (PFS), and secondary objectives included overall response rate (ORR), disease control rate (DCR) and overall survival (OS). Among all the patients, the total mutation rate of EGFR gene was 45.04%, major occurred in 19 exon (40.19%) and 21 exon (48.80%), respectively. There was great difference in gender, smoking status, TNM stage among patients with 19 exon, 21 exon and other mutation of EGFR (All P < 0.05). The ORR (34.31% vs. 28.57%, 21.74%) and DCR (73.53% vs. 69.05%, 56.52%) in patients with 21 exon mutation was significantly higher than patients with 19 exon or other mutations. After three-year follow-up, the median PFS was 7.9 months in the 21 exon group, 6.4 months in the 19 exon group and 5.1 months in the other mutation group (P < 0.05). And the median OS in patients with EGFR 21 exon mutation was significantly higher than those of patients with EGFR 19 exon or other mutations. In conclusion, applied with chemotherapy and EGFR-TKI, Chinese NSCLC patients with EGFR gene 21 exon mutation could have better clinical response and long-term survival than those with other kinds of mutation.