EGFR status evaluation by liquid biopsy during first-line therapy in patients with advanced NSCLC.

Abstract

e20524 Background: over the past decade, personalized management based on the molecular features of tumours in patients with advanced non small-cell lung cancer (NSCLC) has entered routine clinical practice. The poor performance of many advanced NSCLC patients may limit invasive biopsies. The liquid biopsy is a diagnostic procedure performed on cancer-derived material obtained in blood samples. In this abstract, we will describe our experience with liquid biopsies. Methods: In the Reggio Emilia Clinical Cancer Centrefrom March 2016 to December 2016, 42 patients with advanced NSCLC were analyzed that had had or had already started first line therapy. The liquid biopsy was repeated at each imaging response evaluation by thoracic-abdominal compound tomography (CT) scan performed every 3 months. In the liquid biopsy, the mutational status of EGFR was analyzed with real time PCR (KIT cobas EGFR mutation test v2 CE-IVD Roche); in tissue, it was evaluated by pyrosequencing. Results: 21/42 liquid biopsies were EGFR-mutated (12/21 eson 19 and 9/21 eson 21). In 3/21 (14.3%) cases, the tissue biopsies showed wild type (WT) EGFR. 6 liquid biopsies were also performed at time 0 (diagnosis). All liquid biopsies of EGFR WT remained WT during treatment and imaging evaluation. The median number of liquid biopsy tests for patients was 2 (range 1-3). In 4/21 cases, T790M was performed: 3 cases in both liquid biopsies and tissue, and 1 case in tissue but not in liquid biopsy. TKi therapy was ineffective in this patient with T790M mutation detected in tissue, but not in liquid biopsy. In all patients, the disappearance of the T790M mutation during TKi therapy was related to disease progression. In 11 cases, modification of EGFR mutation status during treatment anticipated CT scan evidence of disease progression (median = three months). Conclusions: the liquid biopsy is an excellent resource. In our experience the liquid biopsy is the sensitive method of choice during treatment of advanced NSCLC patients. EGFR modification status during TKi therapy showed advanced disease progression.