Detection of sensitizing and resistance EGFR mutations from circulating tumor DNA (ctDNA) in blood using multiplexed next-generation sequencing in patients with advanced EGFR-mutant lung adenocarcinoma.

Abstract

8093 Background: Analysis of tumor biopsies obtained after the development of acquired resistance (AR) to EGFR tyrosine kinase inhibitors can contribute to the understanding of resistance mechanisms, but requires an invasive procedure and only provides data on a single site of disease at one timepoint. We developed a next-generation sequencing method that employs novel error-suppression techniques to measure tumor-specific mutations in plasma at levels as low as 1 variant in 5,000. Here we report on the detection of sensitizing EGFR mutations and the emergence of the T790M resistance mutation in ctDNA and in tumor specimens. Methods: We collected plasma samples from patients (pts) with advanced EGFR-mutant lung adenocarcinoma. When feasible, serial plasma samples were collected during treatment and repeat tumor biopsies were performed at AR. Plasma was analyzed using error-suppressed deep sequencing to quantify point-mutations and insertions/deletions in multiple genes that are commonly mutated in lung cancer, including EGFR. Results: Plasma samples were obtained from 52 pts with known activating EGFR mutations. Thirty-two pts had serial samples, allowing monitoring of mutant DNA levels and detection of the emergence of new mutations in the plasma. Of the 31 pts who had a repeat biopsy, the T790M mutation was found in 15 (48%) in the tumor at AR. Data for the ctDNA and repeat tumor biopsy results for the first 5 pts tested in this cohort are presented in the Table. Conclusions: Detection of EGFR sensitizing and resistance mutations in ctDNA from the plasma using multiplexed next generation sequencing is feasible and shows a high concordance with results from tumor biopsy. This novel method using plasma may allow for earlier identification of resistance in pts treated with targeted therapy without the need for invasive biopsies. Pt # Source of DNA Sensitizing EGFR mutation EGFR T790M resistance mutation Exon 19 del L858R 1 Lymph node - + - Plasma - + - 2 Lymph node + - + Plasma + - + 3 Pleural fluid + - + Plasma + - + 4 Neck mass - + - Plasma - + - 5 Liver mass + - + Plasma + - -