A seductive vision for the future of clinical oncology permeates the popular press and marketing materials from hospitals and companies. It goes by a variety of names, such as personalized or precision cancer medicine, and promises that identifying genetic alterations in a patient’s cancer will guide the selection of treatments that produce clinical responses with minimal toxic effects.1 This vision is based on the striking success of a handful of targeted therapies whose efficacies are predicted by genetic biomarkers.2-5 While the number of patients who derive clinical benefit from analyzing their tumor genomes is currently quite small, the scientific rationale is compelling and describes a “brave new world” for cancer patients.