Abstract 3192: Liquid biopsies for molecular profiling of mutations in non-small cell lung cancer patients lacking tissue samples
Authors: Remon Jordi , Soria Jean Charles , Planchard David , Jovelet Cecile , Pannet Chloe , Lacroix Ludovic , Gazzah Annas , Lawson Andrew , Smalley Sarah , Howarth Kenth , Gale David , Green Emma , Plagnol Vincent , Rosenfeld Nitzan , Oulassen Ken , Chaput Nathalie , Besse Benjamin 
Published: July 2016

Abstract
Introduction: Approximately 30% of patients with an adenocarcinoma of the lung have an actionable driver mutation. Further understanding the molecular mechanisms of acquired resistance to targeted therapies provides key information for determining subsequent treatment options. Access to tumor tissue to perform either the initial molecular profile or at the point of acquired resistance, however, is often limited. Circulating tumor DNA (ctDNA) can be used as a minimally invasive method for the detection and quantification of molecular abnormalities. We performed a prospective study to assess molecular alterations in the ctDNA of NSCLC patients in whom the initial molecular profile or profile at acquired resistance was unknown due to lack of tumor tissue biopsy or insufficient cellularity in the biopsy.
Methods: Plasma samples were collected from 52 pre-treated advanced NSCLC patients at the Gustave Roussy. DNA was extracted from &lt; 5 ml of plasma and analysed using Inivata's enhanced TAm-SeqTM assay covering regions from 35 cancer-related genes. Sequences were generated using Illumina sequencing. We also analysed plasma taken following treatments prescribed after the original molecular profile detected using plasma ctDNA.
Results: From July 2015 to October 2015, 52 patients were included (63% female, 37% never-smoker, 95% diagnosed with an adenocarcinoma subtype, 95% with stage IV disease, and 54% had EGFR mutant tumors of which 68% had mutations in exon 19 and 32% had mutations in exon 21). ctDNA profiling was successfully performed for all patients, and mutations were detected in 38 of 52 patients. The median number of mutations detected in plasma samples was 1. Within the EGFR mutant subpopulation, T790M mutations were identified including 8 acquired cases (with a concomitant C797S mutation in 1 case) and 1 primary T790M mutation. Of these patients, 5 started personalised treatment with AZD9291 based on the results of ctDNA analysis. In the other 18 patients with EGFR mutant tumors, no acquired mutations associated with resistance were detected. Other results encompassed: 2 plasma samples with EGFR mutation exon 18 (G719A, G719C) leading to initiation of afatinib in one case, 1 case with EGFR mutation exon 21 (L861Q), 1 patients with ERBB2 exon 20 insertion, 3 KRAS mutant detected in plasma (G12C, G12S, G12F), 2 STK11 mutant samples, and 1 patient with a MET mutation (exon 14) who subsequently started crizotinib.
Conclusions: ctDNA analysis with Inivata's enhanced TAm-Seq™ provides an alternative method of ‘liquid biopsy’ for obtaining molecular profile of mutations present in NSCLC patients in the absence of an invasive tissue biopsy. Liquid biopsy identified cancer mutations in 73% of the study population, and 18% of those patients subsequently received treatment tailored to the plasma ctDNA detected mutations. An update on the analysis of 75 patients will be presented during the conference.
Citation Format: Jordi Remon, Jean Charles Soria, David Planchard, Cecile Jovelet, Chloe Pannet, Ludovic Lacroix, Annas Gazzah, Andrew Lawson, Sarah Smalley, Kenth Howarth, David Gale, Emma Green, Vincent Plagnol, Nitzan Rosenfeld, Ken Oulassen, Nathalie Chaput, Benjamin Besse. Liquid biopsies for molecular profiling of mutations in non-small cell lung cancer patients lacking tissue samples. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3192.