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

Xue Yang,Zhijie Wang,Xin Ye,Tongtong An,Jie Wang,Meina Wu,Hua Bai,Minglei Zhuo,Jun Zhao,Yun Sun,Jianchun Duan

doi:10.18632/oncotarget.8021

Abstract

PurposeWe 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.ResultsDetection 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.MethodsSeventy-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.ConclusionsDynamic 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.

Highlights

Great advances have been made in the treatment of non-small cell lung cancer (NSCLC) over the past 40 years
Methods for detecting mutations have been investigated in other specimens that can be acquired and dynamically; examples include the use of specimens like plasma [11,12,13,14,15], pleural fluid [15,16,17], and sputum [18, 19], among which plasma testing has been identified as the most promising tool in EGFR mutation analysis [11, 20]
Seventy-three patients from Peking University Cancer Hospital diagnosed with lung adenocarcinoma, including 29 male and 44 female patients, were enrolled in the study

Summary

Introduction

Great advances have been made in the treatment of non-small cell lung cancer (NSCLC) over the past 40 years. The discovery of oncogenic drivers such as EGFR (epidermal growth factor receptor) has enabled a new and increasingly efficacious phase in cancer treatment [1,2,3,4]. Clinical monitoring molecular resistance through second www.impactjournals.com/oncotarget biopsy of tumor tissues can be challenging. Owing to spatial and temporal heterogeneity, molecular detection methods that use initial tissue samples are not appropriate for therapeutic guidance throughout the entire process of treatment, especially after disease progression. Methods for detecting mutations have been investigated in other specimens that can be acquired and dynamically; examples include the use of specimens like plasma [11,12,13,14,15], pleural fluid [15,16,17], and sputum [18, 19], among which plasma testing has been identified as the most promising tool in EGFR mutation analysis [11, 20]

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