Abstract

Liquid Biopsy Tests Move Towards Routine Patient Care and Management

Walter Koch, Vice President, Roche Molecular Systems

Over the past decade several tissue-based companion diagnostic assays have gained FDA approval in conjunction with targeted cancer therapies, resulting in improved treatment options for many cancer patients.  Despite various international guidelines, not all patients are tested, due in part to limited tissue availability, or health status limits on acquiring a re-biopsy sample.  This has spurred development of so-called liquid biopsy tests which use body fluids such as plasma to ascertain tumor mutational status in circulating cell free DNA originating from tumors, or circulating tumor cells.  On June 1, 2016 the FDA-approved the cobas® EGFR Mutation Test v2 real-time PCR test for the qualitative detection of defined mutations of the epidermal growth factor receptor (EGFR) gene in non-small cell lung cancer (NSCLC) patients. For the first time the test can be used with both formalin-fixed paraffin-embedded tumor tissue (FFPET) as well as circulating-free tumor DNA (cfDNA) from plasma derived from EDTA anti-coagulated peripheral whole blood.  The test is indicated as a companion diagnostic to aid in selecting NSCLC patients for treatment with the targeted therapies including TARCEVA®. This milestone heralds the first of many to come that will provide additional opportunities for cancer patients to be evaluated with blood samples for treatment with targeted therapies.  Analogous to HIV viral load testing, further clinical development will likely extend the use of such blood tests to allow monitoring of initial drug response as well as disease progression and/or development of specific resistance mutations.  Collectively these advances promise to provide important clinical information not easily obtained by repeat tissue biopsy approaches.