- Advances in "omics" technology and targeted therapeutic molecules are together driving the incorporation of molecular-based diagnostics into the care of patients with cancer. There is an urgent need to assess the efficacy of therapy determined by molecular matching of patients with particular targeted therapies. WINTHER is a clinical trial that uses cutting-edge genomic and transcriptomic assays to guide treatment decisions. Through the lens of this ambitious multi-national trial (five countries, six sites) coordinated by the Worldwide Innovative Networking (WIN) Consortium for personalized cancer therapy, we discovered key challenges in initiation and conduct of a prospective, omically-driven study. To date, the time from study concept to activation has varied between 19 months at Gustave-Roussy Cancer Campus in France to 30 months at the Segal Cancer Center, McGill University (Canada). It took 3+ years to be able to activate U.S. sites due to national regulatory hurdles. Access to medications proposed by the molecular analysis remains a major challenge, since their availability through active clinical trials is highly variable over time within sites and across the network. Rules regarding off-label use of drugs, or drugs not yet approved at all in some countries, pose a further challenge, and many biopharmaceutical companies lack a simple internal mechanism to supply the drugs even if they wish to do so. These various obstacles should be addressed in order to test and then implement precision medicine in cancer. © The Author 2015. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: email@example.com.