A new study shows that a test physicians commonly use to guide chemotherapy for patients with breast cancer after surgery may also help them decide whether radiation therapy may be of benefit. Results published by Wendy A. Woodward, MD, PhD, and colleagues in JAMA Oncology suggest patients with an intermediate or high 21-gene recurrence score are more likely to see their cancer recur in the breast and nearby lymph nodes and, thus, could benefit from radiation.

The 21-gene recurrence score test—sold as the Oncotype DX Breast Recurrence Score Test—is a personalized analysis of the activity of 21 genes found in a patient’s breast tumor tissue. 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.

Current Study Methods

Wendy A. Woodward, MD, PhD

Lead investigator Dr. Woodward and her team wanted to see if the 21-gene recurrence score could also be useful in predicting the local breast cancer recurrence that radiation can prevent. Radiation is much more targeted than chemotherapy, focusing on specific areas in and around the breast. The team was particularly interested in how recurrence scores might help add to the clinical tools that currently guide radiation for patients, especially when the need isn’t clear.

To find out, investigators examined data generated by S8814, a long-closed SWOG trial that compared postsurgery treatments in postmenopausal women with breast cancer. In this randomized trial, postmenopausal women with node-positive breast cancer were randomly assigned to one of three treatments. Physicians recommended radiotherapy based on clinical factors, such as tumor size and the number of lymph nodes that contain cancer.

As part of S8814, 367 patients took the 21-gene recurrence score test. The investigators reviewed all these records to see which patients had radiation therapy and which had locoregional recurrence. The team was left with a pool of 316 patient records. They logged every patient’s recurrence score, as well as whether and when locoregional recurrence occurred.

Findings

After a median of 8 years of follow-up, 34 patients went on to have a locoregional recurrence event—27 with intermediate or high recurrence scores and 7 with low recurrence scores. Regardless of other factors, such as number of cancer-positive lymph nodes, the recurrence score proved to be an independent predictor for locoregional recurrence.

“We believe these data support using recurrence scores, along with standard clinical factors like age or tumor size, to determine risk of recurrence and radiotherapy decisions for patients,” said Dr. Woodward. “Our findings are clearly limited, as we had some small patient numbers and looked at data retrospectively. But these results provide additional evidence of the value of this test in node-positive patients, and they suggest it might be possible to skip radiation in patients with low recurrence scores and one to three cancer-positive nodes, a question now being rigorously tested in TAILOR RT. There are large clinical trials going on looking at radiation care for patients [with breast cancer], like TAILOR RT, and I encourage people to enroll. The more data we have, the more we’ll know how to use this new precision medicine tool.”

The Canadian Cancer Trials Group, with co-sponsorship by the National Cancer Institute, is enrolling patients on the TAILOR RT trial, which will confirm whether recurrence score alone can identify low-risk, node-positive patients with breast cancer who do not need radiation.

The study authors concluded, “This study found that higher recurrence scores were associated with increased locoregional recurrence after adjustment for treatment, type of surgical procedure, and number of positive nodes. This finding suggests that the recurrence score may be used, along with accepted clinical variables, to assess the risk of locoregional recurrence during radiotherapy decision-making.”

Disclosure: Funding for this SWOG study comes from National Institutes of Health through the National Cancer Institute, and in part by Genomic Health, Inc. For full disclosures of the study authors, visit jamanetwork.com.