Oncotype DX is intended for patients with node-negative, estrogen receptor-positive breast cancer who are likely to be treated with hormonal therapy. Approximately half of the 230,000 patients diagnosed with breast cancer in the United States each year fall into this category, and are frequently offered treatment with chemotherapy, a widely used treatment with considerable side effects. Clinical studies show that chemotherapy improved patient survival rates in only 4 out of 100 patients, yet thousands of women continue to elect this costly and toxic treatment with only limited information about whether they might respond to it. A recent study demonstrated that [...]