Quantification of mutant alleles in circulating tumor DNA can predict survival in lung cancer

// Xue Yang 1, * , Minglei Zhuo 1, * , Xin Ye 2 , Hua Bai 1 , Zhijie Wang 1 , Yun Sun 2 , Jun Zhao 1 , Tongtong An 1 , Jianchun Duan 1 , Meina Wu 1 , Jie Wang 1 1 Department of Thoracic Medical Oncology, Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Peking University Cancer Hospital and Institute, Beijing, China 2 Asia and Emerging Markets Innovative Medicine of AstraZeneca R & D, Shanghai, China * These authors contributed equally to this work Correspondence to: Jie Wang, e-mail: zlhuxi@163.com Keywords: non-small-cell lung cancer, epidermal growth factor receptor, circulating tumor DNA, droplet digital PCR, next-generation sequencing Received: August 25, 2015      Accepted: February 15, 2016      Published: March 10, 2016 ABSTRACT Purpose: We aimed to investigate the feasibility of droplet digital PCR (ddPCR) for the quantitative and dynamic detection of EGFR mutations and next generation sequencing (NGS) for screening EGFR-tyrosine kinase inhibitors (EGFR-TKIs) resistance-relevant mutations in circulating tumor DNA (ctDNA) from advanced lung adenocarcinoma (ADC) patients. Results: Detection limit of EGFR mutation in ctDNA by ddPCR was 0.04%. Taking the EGFR mutation in tumor tissue as the golden standard, the concordance of EGFR mutations detected in ctDNA was 74% (54/73). Patients with EGFR mutation in ctDNA ( n = 54) superior progression-free survival (PFS, median, 12.6 vs. 6.7 months, P < 0.001) and overall survival (OS, median, 35.6 vs. 23.8 months, P = 0.028) compared to those with EGFR wild type in ctDNA ( n = 19). Patients with high EGFR-mutated abundance in ctDNA (> 5.15%) showed better PFS compared to those with low EGFR mutated abundance (≤ 5.15%) (PFS, median, 15.4 vs. 11.1 months, P = 0.021). NGS results showed that 66.6% (8/12) total mutational copy number were elevated and 76.5% (26/34) mutual mutation frequency increased after disease progression. Methods: Seventy-three advanced ADC patients with tumor tissues carrying EGFR mutations and their matched pre- and post-EGFR-TKIs plasma samples were enrolled in this study. Absolute quantities of plasma EGFR mutant and wild-type alleles were measured by ddPCR. Multi-genes testing was performed using NGS in 12 patients. Conclusions: Dynamic and quantitative analysis of EGFR mutation in ctDNA could guide personalized therapy for advanced ADC. NGS shows good performance in multiple genes testing especially novel and uncommon genes.