A new study shows that a test physicians commonly used to guide chemotherapy treatment for post-breast cancer surgery patients may also help them decide whether radiation therapy may be of benefit.

Known as the 21-gene recurrence score, the test is a personalized analysis of the activity of 21 genes found in a patient's breast tumor tissue. The score can be used to predict whether, after undergoing surgery, that patient's breast cancer is likely to return in another part of their body, like the bones or lungs, and whether that patient will likely benefit from chemotherapy treatment.

Study results suggest patients with an intermediate or high 21-gene recurrence score are more likely to see their cancer return to the breast and nearby lymph nodes and, thus, could benefit from radiation. Findings appear today in JAMA Oncology. The study was conducted by the SWOG Cancer Research Network, a cancer clinical trials network funded by the National Cancer Institute (NCI), part of the National Institutes of Health, and part of the oldest and largest publicly funded research network in the nation.

The Canadian Cancer Trials Group, with co-sponsorship by the NCI, is enrolling patients on a trial called TAILOR RT, which will confirm whether the recurrence score - all by itself - can identify low risk node positive patients who do not need radiation. Because randomized trials represent the gold standard in clinical research, TAILOR RT results could change the standard of cancer care. Until that data is in, the SWOG findings provide evidence that the recurrence score can be an effective, additional tool - along with tumor size or stage - that physicians can use to determine whether to recommend radiation therapy, particularly for patients whose cancer presentation makes the need for radiation uncertain.

"For a decade, radiation oncologists have been banging on the doors of precision medicine, looking for genomic tools they can use to personalize treatment for their patients," said Wendy Woodward, MD, PhD, lead investigator of the SWOG study and chief of the clinical breast radiotherapy service at the University of Texas M.D. Anderson Cancer Center. "Radiation oncologists want these tools because they can help their patients. Radiation treatment can help wipe out local disease, saving or lengthening a patient's life. And omitting radiation treatment could spare other patients pain, time, and cost."

The 21-gene recurrence score test is sold as the Oncotype DX Breast Recurrence Score and was developed by the California-based company Genomic Health, Inc. In multiple research studies, the test has been proven to predict the likelihood of disease recurrence - and chemotherapy benefit - in patients with invasive, early-stage breast cancer.

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