The findings can help oncologists and breast cancer patients make decisions about the best course of treatment.

Breast cancer is the second most common type of cancer in the United States. Half of thecases involve tumors that contain receptors for the hormones estrogen and/or progesterone (hormone receptor (HR)-positive), have very little of a growth-related protein called HER2 on the surface (HER2-negative), and have not moved to the lymph nodes (axillary lymph node-negative).

Many women with this type of breast cancer are advised to receive chemotherapy in addition to radiation and hormonal therapy. Treatment recommendations are based on their risk for a breast cancer recurrence. There are several commercially available tests to predict breast cancer recurrence. The Oncotype DX test (Genomic Health, Inc.) assesses 21 genes to assign a risk score for cancer recurrence on a scale of 0–100. Based on earlier evidence, women with a score in the low-risk range (0–10) can receive hormone therapy only. Those with a score in the high-risk range (26 and above) should be treated with hormone therapy and chemotherapy. For women with an intermediate level of risk for recurrence (11–25), however, the best course of action hasn’t been clear.

To investigate treatment options for women with intermediate risk levels, a clinical trial called TAILORx was designed to follow more than 10,000 women worldwide who had early-stage, HR-positive, HER2-negative, axillary lymph node-­negative breast cancer. The study was supported in part by NIH’s National Cancer Institute (NCI).

When the women were enrolled, from April 2006 to October 2010, their tumors were analyzed using the Oncotype DX test. Those in the low-risk range received hormone therapy only. Those in the high-risk range were treated with hormone therapy and chemotherapy. Women in the intermediate range were randomly assigned to receive hormone therapy with chemotherapy or hormone therapy alone. Results were published online in theNew England Journal of Medicineon June 3, 2018.

The rates of women who survived, or didn’t develop a recurrence or a second primary cancer, were very similar in both groups in the intermediate risk category. Five years after treatment, the rate of invasive disease-free survival was 92.8% for hormone therapy alone and 93.1% for those who also had chemotherapy. At nine years, the rate was 83.3% for those with hormone therapy alone and 84.3% for the group that had both therapies.

Some premenopausal women and those younger than 50 years old at the higher end of the intermediate-risk range (16–25) showed a small benefit from chemotherapy. However, it’s unclear why. Women in this group should consider chemotherapy with their doctor.

“The new results from TAILORx give clinicians high-quality data to inform personalized treatment recommendations for women,” says lead researcher Dr. Joseph A. Sparano of the Albert Einstein Cancer Center and Montefiore Health System. “These data confirm that using a 21-gene expression test to assess the risk of cancer recurrence can spare women unnecessary treatment if the test indicates that chemotherapy is not likely to provide benefit.”