Liquid biopsy: Safety and efficacy in a tool for molecular profiling of advanced non-small cell lung cancer (NSCLC).

Abstract

e21506 Background: Non-small cell lung cancer (NSCLC) is the most common type of lung cancer with a broad spectrum of targeted therapies already available or in clinical trials. Among the NSCLC patients, 23% to 25% harbor a mutation in a gene associated with approved or emerging targeted therapy. These therapies have changed the therapeutic landscape of NSCLC with significantly improved clinical outcomes in advanced metastatic NSCLC patients. It is imperative to test for these gene alterations in order to identify patients who could potentially benefit from these efficacious targeted therapies and to avoid therapies unlikely to provide clinical benefit. A major limitation in obtaining molecular testing occurs when minimally invasive techniques are used to obtain tissue sample resulting in insufficient yield for testing. In such cases, the utilization of circulating tumor DNA (ctDNA), commonly known as liquid biopsy, has proven very beneficial. In a study utilizing ctDNA, increased detection rates were found when using ctDNA in addition to tissue testing and a > 98.2% concordance rate was found. We report results of 40 NSCLC patients from our institute who had liquid biopsy with or without tissue profiling done. Methods: We molecularly profiled 40 newly diagnosed advanced NSCLC patients using both tissue and liquid biopsies. Tissue was assayed using the John Hopkins university molecular panel and liquid biopsies were performed by Biocept. Results: 14 out of 40 (35%) patients had insufficient or no tissue for molecular testing. Concordant results were found in 17 out of the 26 (65.4%) patients who had both tissue and liquid molecular testing done. Liquid Biopsy detected additional mutations in 5 (19.2%) patients which were not picked up on tissue and led to change in management in 4 patients. 12 out of 40 (30%) patients had repeat liquid biopsies done at progression of disease with new mutations detected on 4 patients revealing resistance to current treatment and change in treatment. Conclusions: Liquid Biopsy reveals high concordance rates with tissue genotyping and increases rate of detection of targetable mutations in NSCLC. It offers a safe and effective alternative when additional tissue is needed to identify genetic mutations.