Breast cancer is the most common cancer among US women, with more than 230,000 new diagnoses and 40,000 deaths each year, along with decrements in quality of life. Half of all newly-diagnosed patients are affected with estrogen-receptor positive, early-stage disease. Clinical guidelines for these women integrate genomic tumor profiling tests such as the Oncotype DX® Recurrence Score to refine recurrence estimates and systemic therapy selection when combined with existing markers. Thousands of women receive testing each year. While these women should all receive hormonal therapy, guidelines suggest that the 25% with a high Score benefit from additional chemotherapy and the 50% with a low Score can safely avoid chemotherapy. Appropriate treatment for the 25% of women with intermediate Recurrence Scores remains unclear until clinical trial (TAILORx) results are released in the next year.