The trial included women age 18-75 with estrogen-receptor positive, lymph node negative stage I or II breast cancer, all of whom met standard clinical guidelines for receiving chemotherapy in order to reduce the risk of cancer recurrence after surgery. All patients had an Oncotype DX® Recurrence Score® test performed on their tumor sample, which is a gene expression assay test available from Genomic Health, Inc. The test measures the activity level of a panel of genes within the tumor sample, and the result correlates with the likelihood of having breast cancer recurrence. Tumors with a low Recurrence Score are likely to be cured with surgery and hormonal therapy alone. Tumors with a high Recurrence Score have a high recurrence rate with hormonal therapy and require chemotherapy to reduce the post-surgery recurrence risk. Women in the study will be followed for up to 20 years. “The Recurrence Score test results provided a clear treatment path for about one-third of women who participated in the trial because their score was either low or high.” said Joseph Sparano, MD, the principal investigator of the trial. “The remaining two-thirds of women with a mid-range score tumor were the focus of this trial because we have strong reason to believe that they don’t benefit from chemotherapy. We needed a large-scale clinical trial to prove whether chemotherapy is benefiting this group, or not.”