The document provides an overview of genomics in breast cancer and summarizes the Oncotype DX genomic assay. It discusses how the assay analyzes the expression levels of 21 genes in breast tumor tissue to provide a Recurrence Score that quantifies a patient's risk of recurrence and predicts who will benefit from chemotherapy. Clinical studies have shown the assay stratifies patients into low, intermediate, and high risk groups and identifies those unlikely to benefit from chemotherapy while high risk patients see significant reduction in recurrence with chemotherapy. The assay is recommended in clinical guidelines and widely covered by insurance.