P2.01-62 Extracellular Vesicle-Based Egfr Genotyping in Bronchoalveolar Lavage Fluid from Non-Small Cell Lung Cancer Patients

Abstract

Liquid biopsies for EGFR genotyping using plasma cell-free DNA (cfDNA) have limited value due to low sensitivity. Extracellular vesicles (EV) have been proven to contain mutant EGFR DNA in bronchoalveolar lavage fluid (BALF) from non-small cell lung cancer (NSCLC) patients. As an alternative to plasma liquid biopsies using cfDNA, we investigated the feasibility of EV-based liquid biopsy for EGFR genotyping using BALF from NSCLC patients, prospectively. EV DNA was extracted from the BALF of NSCLC patients with confirmed tissue/cytology-based EGFR genotyping at initial diagnostic work-up stage. (N=137) The number of patients with stage I, II, III, and IV are 37 (27%), 6 (4.4%), 23 (16.8%), 71 (51.8%), respectively. The patients were selected by favorable demographic data for EGFR mutation. EGFR mutation testing was done by peptide nucleic acid (PNA) clamping-assisted fluorescence melting curve analysis. The overall sensitivity and specificity of EGFR genotyping using BALF EV DNA were 69.5% and 83.3% and the concordance rate was 77.4%. (Kappa=0.534, P=0.000) The sensitivity was significantly increased along with the stage (42.1% in stage I, II, 60.0% in stage III, and 100% in stage IV). Especially, in stage IV disease, BALF EV-based EGFR typing did not miss all of tissue-proven 30 EGFR mutant cases and detected 9 additional mutant cases. Detection of EGFR mutation becomes significantly more sensitive as T stage increases. (T1 = 43.8%, T2 = 75%, T3 and T4 = 100%) Turn-around time (TAT) for EGFR genotyping using BALF EV DNA was 1-2 days, while it takes usually 2 weeks for tissue typing. BALF EV-based EGFR genotyping is a novel and highly promising method with rapid TAT and incredible accuracy in stage IV NSCLC patients. Further research in early stage disease is necessary and the matter of over-detection should be clinically validated by evaluating EGFR-TKI drug response.