P1.15-08 Implementation and Feasibility of the Assessment of EGFR Mutation in NSCLC Using Liquid Biopsy at an Argentinean University Hospital

Abstract

Molecular characterization of lung cancer is standard of care. Almost 85% of NSCLC patients have advanced disease at diagnosis, being a challenge get enough tissue for diagnosis. That' s why using less invasive methods as liquid biopsy by determining cftDNA (circulating free tumor DNA) represents a promising tool. The detection of EGFR mutations in plasma by Therascreen (EGFR RGQ Mutation Kit) showed a sensitivity and specificity of 65.4% and 100 % respectively. It is also useful to detect TKI's resistance previous to clinical progression. The advantages of using PCR, even there are more sensitive methods available, are its simplicity and cost. We will prospectively recruit EGFR mutation-positive (n=40) NSCLC patients. Plasma samples are collected: baseline, after three months of treatment, every six months and at the time of progression. We report our first interim analysis. We evaluate the concordance of EGFRm in tissue and plasma with the implementation of the Therascreen test (Qiagen). We test other available plasma EGFRm detection kit (EGFR Plasma Mutation Analysis Kit, Entrogen) (n=10) Since February 2017, plasma EGFRm status could be determined in 17 out of 22 NSCLC patients with EGFRm in tissue. L858R was present in 9 (53%), del19 in 7 (42%), del19+T790M in 1 (5%). Baseline plasma analyzed with Therascreen and Entrogen kits showed similar sensitivity of 61.1% and 66% respectively. Only 1/11 pt had discordance between both kits (Therascreen negative , entrogen DEL19+T790M ). In 17 analyzed ptes, median age was 59 (51-76) years. Most of the population were women (88%), were never smokers (58%), had stage IV disease (58%). Frequent site of metastasis was bone (n=7). With a median follow up of 18 months (12-23), 7/15 (56%) patients who experienced clinical progression were detected also in plasma. Two patients presented T790M in plasma without evidence of disease progression until last follow-up (July 2018). We also observed two patients with mutations detected out of range to be considered as positive which became positive for these mutations during the follow up. This is the first work showing a cohort of EGFRm patients prospectively analyzed by successive liquid biopsies in a public institution in Argentina. We could successfully obtain cftDNA and analyze it by two commercial kits. The sensitivity of both kits was comparable to previous reports. The study is ongoing and more samples will be analized to shed light about the plasma dynamics of EGFRm related to clinical behavior.