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// Jessica Garcia 1, 2, 3, 4, ** , Eric Dusserre 1, 3, 4, ** , Valerie Cheynet 3, 5 , Pierre Paul Bringuier 6 , Karen Brengle-Pesce 3, 5 , Anne-Sophie Wozny 1, 7 , Claire Rodriguez-Lafrasse 1, 3, 4, 7 , Gilles Freyer 4, 8, 9 , Marie Brevet 4, 6, 9 , Lea Payen 1, 2, 3, 4, 7, * and Sebastien Couraud 4, 9, 10, * 1 Laboratoire de Biochimie et Biologie Moleculaire, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, 69310, Pierre Benite, France 2 Centre de Recherche en Cancerologie de Lyon, INSERM 1052, CNRS 5286, Universite Claude Bernard Lyon 1, Lyon, 69003, France 3 Laboratoire Commun de Recherche Hospices Civils de Lyon – BioMerieux, Centre Hospitalier Lyon Sud, 69310, Pierre Benite, France 4 Institut de Cancerologie des Hospices Civils de Lyon, CIRculating CANcer Program (CIRCAN), 69002 Lyon, France 5 Medical Diagnostic Discovery Department, BioMerieux, 69290 Craponne, France 6 Service d’Anatomie et de Cytologie Pathologiques, Groupement Hospitalier Est, Hospices Civils de Lyon, 69500, Bron, France 7 Faculte de Pharmacie de Lyon (IPSB), Universite de Lyon1, Lyon, 69008, France 8 Service d’Oncologie Medicale, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, Lyon, 69003, France 9 EMR 3738 Ciblage Therapeutique en Oncologie, Faculte de Medecine Lyon Sud, Universite Lyon 1, 69600, Oullins, France 10 Service de Pneumologie Aigue Specialisee et Cancerologie Thoracique, Centre Hospitalier Lyon Sud, Hospices Civils de Lyon, Lyon, 69003, France * Authors share co-senior authorship ** Authors share co-first authorshop Correspondence to: Lea Payen, email: lea.payen-gay@chu-lyon.fr Keywords: lung cancer, EGFR mutation, circulating-free DNA, liquid biopsy, digital PCR Received: December 22, 2016 Accepted: June 26, 2017 Published: September 21, 2017 ABSTRACT Non invasive somatic detection assays are suitable for repetitive tumor characterization or for detecting the appearance of somatic resistance during lung cancer. Molecular diagnosis based on circulating free DNA (cfDNA) offers the opportunity to track the genomic evolution of the tumor, and was chosen to assess the molecular profile of several EGFR alterations, including deletions in exon 19 (delEX19), the L858R substitution on exon 21 and the EGFR resistance mutation T790M on exon 20. Our study aimed at determining optimal pre-analytical conditions and EGFR mutation detection assays for analyzing cfDNA using the picoliter-droplet digital polymerase chain reaction (ddPCR) assay. Within the framework of the CIRCAN project set-up at the Lyon University Hospital, plasma samples were collected to establish a pre-analytical and analytical workflow of cfDNA analysis. We evaluated all of the steps from blood sampling to mutation detection output, including shipping conditions (4H versus 24H in EDTA tubes), the reproducibility of cfDNA extraction, the specificity/sensitivity of ddPCR (using external controls), and the comparison of different PCR assays for the detection of the three most important EGFR hotspots, which highlighted the increased sensitivity of our in-house primers/probes. Hence, we have described a new protocol facilitating the molecular detection of somatic mutations in cancer patients from liquid biopsies, improving their diagnosis and introducing a less traumatic monitoring system during tumor progression.

Non invasive somatic detection assays are suitable for repetitive tumor characterization or for detecting the appearance of somatic resistance during lung cancer. Molecular diagnosis based on circulating free DNA (cfDNA) offers the opportunity to track the genomic evolution of the tumor, and was chosen to assess the molecular profile of several EGFR alterations, including deletions in exon 19 (delEX19), the L858R substitution on exon 21 and the EGFR resistance mutation T790M on exon 20. Our study aimed at determining optimal pre-analytical conditions and EGFR mutation detection assays for analyzing cfDNA using the picoliter-droplet digital polymerase chain reaction (ddPCR) assay. Within the framework of the CIRCAN project set-up at the Lyon University Hospital, plasma samples were collected to establish a pre-analytical and analytical workflow of cfDNA analysis. We evaluated all of the steps from blood sampling to mutation detection output, including shipping conditions (4H versus 24H in EDTA tubes), the reproducibility of cfDNA extraction, the specificity/sensitivity of ddPCR (using external controls), and the comparison of different PCR assays for the detection of the three most important EGFR hotspots, which highlighted the increased sensitivity of our in-house primers/probes. Hence, we have described a new protocol facilitating the molecular detection of somatic mutations in cancer patients from liquid biopsies, improving their diagnosis and introducing a less traumatic monitoring system during tumor progression.