Keith Kerr, MB, ChB, FRCPath, FRCPE from the University of Aberdeen, Aberdeen, Scotland talks about the importance of guidelines for the recommendation of best clinical practice. Dr Kerr discusses the 2013 guidelines for molecular testing in advanced non-small cell lung cancer (NSCLC) produced by the College of American Pathologists and the International Association for the Study of Lung Cancer (IASLC). These guidelines focused on testing for EGFR mutations and ALK gene rearrangements in NSCLC. New guidelines are expected to be published in 2017 which will include new biomarkers such as ROS1 fusion proteins. Dr Kerr explains how drugs for some new biomarkers are still to be approved which can make developing guidelines challenging. Recorded at the European Cancer Congress of the European Cancer Organisation (ECCO) 2017 in Amsterdam, Netherlands.