Abstract 2748: Liquid biopsy using extracellular vesicular DNA for EGFR mutation testing in the patients with NSCLC

Abstract

Abstract Background Tumor-derived extracelluar vesicles (EV) have been proved to carry double-stranded DNA including oncogenic mutants and expected to be a novel biomarker in cancer detection. Liquid biopsy using cell-free (cf) DNA for EGFR mutation testing is being actively investigated. In this study, we investigated whether liquid biopsy using EV DNA is superior to cf DNA for EGFR mutation testing in the patients with NSCLC. Methods EV was isolated using ultracentrifugation and confirmed by transmission electron microscopy and zetasizer in 20 plasma samples (all tissue-proven EGFR mutated) and 32 bronchoalveolar lavage fluid (BALF) samples (23 EGFR-mutated including 14 TKI-naïve and 9 TKI resistant, and 9 wild-type). EV and cf DNA was separately extracted from each samples and EGFR mutation testing was performed by peptide nucleic acid (PNA)-clamping method. Results In 20 plasma samples, the concordance rate of EV DNA for tissue EGFR genotyping was 55% (11/20), while 30% (6/20) in cf DNA. In 32 BALF samples, however, the sensitivity, specificity and concordance rate of EV DNA for activating EGFR mutations was 100% (23/23), 100% (9/9), and 100% (32/32), while cf DNA showed 73.9% (17/23), 100% (9/9) and 81.3% (26/32), respectively. The kappa value (p-value) of EV DNA was 1.0 (<0.001), while it was 0.714 (p,0.001) in the case of cf DNA. As for 9 re-biopsy cases for T790M detection in which only 3 patients (33%) was proved as positive T790M, BALF EV DNA identified 2 more T790M patients (total 5 among 9 patients, 56%) without non-matching with tissue typing, while BALF cf DNA found 1 more T790M positive patient with missing 1 tissue proven case (total 3 among 9 patients, 33%) Conclusions Liquid biopsy using EV DNA is significantly superior to cf DNA in both plasma and BALF. A little low sensitivity in plasma EV DNA is supposed to be improved with much more sensitive method such as ddPCR or BEAMing. Liquid biopsy using BALF EV DNA showed almost 100% matching with tissue EGFR typing and seems to be highly promising for T790M detection. A large number of clinical trials should be prompted. Citation Format: Jae Young Hur, Hee Jung Kim, Chang-Min Choi, Jae Cheol Lee, Kye Young Lee. Liquid biopsy using extracellular vesicular DNA for EGFR mutation testing in the patients with NSCLC [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2748. doi:10.1158/1538-7445.AM2017-2748