Noninvasive EGFR testing in plasma circulating free DNA (cfDNA) by a new diagnostic method to detect point mutations, deletions and insertions associated to non small cell lung cancer: CLART CMA EGFR LB.

Abstract

e20008 Background: Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are current treatments for advanced non-small cell lung cancer (NSCLC) with activating EGFR gene mutations. Histological samples are the standard tumor materials for EGFR mutation analysis. However, the accessibility of tumor samples is not always possible in advanced NSCLC patients. Moreover, a high percentage of EGFR mutated NSCLC patients will develop resistance to EGFR-TKIs such as T790M mutation. CLART CMA EGFR LB is a novel diagnostic assay able to detect 39 high-prevalence mutations associated with sensitivity or resistance to tyrosine kinase inhibitor treatment. Methods: A highly sensitive and specific method was developed for detection of EGFR mutations (G719X, T790M, L858R, L861Q, insertions in exon 20, and deletions in exon 19) in plasma samples (cfDNA). CLART CMA EGFR LB is based on a preamplification step with a multiplex ARMS-PCR and microarray detection system. Clinical testing was performed using 51 clinical plasma samples: 27 contained L858R, T790M, and deletions in exon 19; 24 contained wild type alleles. 20 samples were cross checked by next generation sequencing performed on the PGM platform (Ion Ampliseq™ Custom, deep-coverage 15000x). Results: Analytical sensitivity was assessed using recombinant plasmids, results ranged between 10-1000 copies/5µl for all mutations. cfDNA from cell lines with the mutations L858R, T790M and deletions in exon 19 at different frequencies (cfDNA Reference Standard, Horizon) were assessed. The system was able to detect the mutations present in a frequency of 2%. The analysis of 51 samples allowed establishing the diagnostic sensitivity and specificity in 93.33% and 100% respectively. CLART CMA EGFR LB showed similar analytical and diagnostic sensitivity than NGS for detecting L858R, T790M and deletions in exon 19. Conclusions: Our data support the use of CLART CMA EGFR LB for clinical testing prior to the selection of the appropriate treatment in NSCLC, monitoring the patient evolution and the emergence of resistance mutations such as T790M in plasma samples.