Roadmap for developing and validating therapeutically relevant genomic classifiers.

Oncologists need improved tools for selecting treatments for individual patients. The development of therapeutically relevant prognostic markers has traditionally been slowed by poor study design, inconsistent findings, and lack of proper validation studies. Microarray expression profiling provides an exciting new technology for relating tumor gene expression to patient outcome, but it also provides increased challenges for translating initial research findings into robust diagnostics that benefit patients and physicians in therapeutic decision making. This article attempts to clarify some of the misconceptions about the development and validation of multigene expression signature classifiers and highlights the steps needed to move genomic signatures into clinical application as therapeutically relevant and robust diagnostics.