The Evolving Role of Companion Diagnostics for Breast Cancer in an Era of Next-Generation Omics.

A companion diagnostic is a test for a specific biomarker-approved by the United States Food and Drug Administration-qualifying a patient to receive a specific, associated therapy. As interest has grown in precision medicine over the past decade, the principle of companion diagnostics has gained increasing purchase among laboratory professionals, clinicians, regulators, and even patients. The evolution of the biomarkers used to stratify and treat breast cancer illustrates the history of companion diagnostics and provides a lens through which to examine potential challenges. As new targeted therapies and corresponding biomarkers accumulate, algorithms for diagnosis and treatment necessarily become lengthier and more complex. To accommodate future needs of breast cancer patients, the companion diagnostic model will continue to adapt and evolve.