Diagnostic tests based on gene expression profile in breast cancer: from background to clinical use.

Breast cancer is a complex disease with heterogeneous presentation and clinical course. The last decade has witnessed the development, commercialization, and increasing use of multigene assays, designed to support physicians and patients in clinical decision making in early-stage breast cancer. These include Oncotype DX®, MammaPrint®, and Prosigna™ assays. The assays differ in the technological platforms used for assessment of gene expression, in the number of genes and in the specific genes that are being tested, in the patient populations used for their development and validation, and in their clinical utility. This review focuses on these three commercialized assays, their development, validation, and clinical utility. The review also addresses ongoing prospective trials investigating these assays and health-economic considerations relating to their use.