ctDNA assessment of EGFR mutation status in Chinese patients with advanced non-small cell lung cancer in real-world setting

Background: The prevalence of EGFR mutations in circulating free tumor-derived DNA (ctDNA) was still unknown in China. This large-scale study (NCT02623257) aimed to explore the prevalence of epidermal growth factor receptor (EGFR) mutations and determine the correlation of EGFR mutation status with clinical characteristics. Methods: Plasma DNA samples from 1,001 patients with stage III/IV NSCLC who received <= 1st line chemotherapy were collected from 65 hospitals. EGFR mutations were tested by amplification refractory mutation system (ARMS) method. The EGFR mutation rate was calculated and the associations between EGFR status and patients' demographic data, disease status as well as treatment pattern were explored. Results: EGFR mutations were detected in 251 of 1,001 (25.1%) patients, 26.8% in adenocarcinoma and 11.7% in squamous carcinoma. A total of 189 harbored sensitizing- mutations alone, 28 had resistance mutations alone, 3 had a combination of activating mutations, and 31 had a combination of activating and resistance mutations. Higher detection rate was observed in chemotherapy-naive patients than those received 1st line chemotherapy (27.0% vs. 18.0%; P=0.006). Of which, the mutation rate of exon 19 deletion was 9.31% for naive patients and 7.37% for the 1st chemotherapy patients; while the mutation rate of L858R decreased obviously from 10.20% (naive) to 3.69% (1st line). We also noticed the mutation rate was 37.1 % in patients with >= 2 organ metastases. Multivariate analysis showed female, chemothcrapy-naive, or >2 metastatic organs patients had higher FGFR mutation rate. Conclusions: ctDNA based EGFR mutation test is feasible and could be a surrogate when tissue biopsy is not available.