New research found that older patients with hormone receptor (HR)-positive breast cancer who did not receive radiation therapy after breast-conserving surgery had higher rates of local recurrence but similar 10-year survival rates compared with patients who had postoperative radiation therapy, according to data presented at the 2020 San Antonio Breast Cancer Symposium.

“Over half the patients diagnosed with breast cancer in developed countries are over the age of 65 years,” said Ian Kunkler, FRCPE, professor of clinical oncology at the Western General Hospital at the University of Edinburgh, in a press release. “We were interested in determining whether older patients with low-risk breast cancer could be spared radiation therapy.”

The data were from the PRIME II study, which enrolled 1326 patients with non-metastatic HR-positive breast cancer. All patients were at least 65 years of age, had undergone breast-conserving surgery, and were receiving adjuvant hormone therapy. Although this population typically has less aggressive breast cancer diagnoses, the authors noted that most patients who undergo breast-conserving surgery continue to be treated with whole breast radiation therapy after surgery.

In the study, patients were randomly assigned to either receive or not receive radiation therapy after surgery. The authors previously reported greater rates of local recurrence in patients who did not receive radiation therapy but not significant differences in overall survival, distant metastases, or new breast cancers between the 2 arms after 5 years. The newest data are results from a 10-year follow-up.

According to a press release, the rate of local recurrence after 10 years was significantly greater in patients who did not receive radiation therapy compared with patients who did (9.8% vs 0.9%, respectively).

Although postoperative radiation therapy affected the risk of local recurrence, it did not significantly impact certain other clinical outcomes. After 10 years, patients who did not receive radiation therapy had similar rates of distant metastasis (1.4% vs 3.6%), recurrence in the opposite breast (1% vs 2.2%), and overall survival (80.4% vs 81%) as patients who did receive radiation therapy. Most deaths were due to reasons other than breast cancer, according to the press release.

“We found that omitting postoperative radiation therapy did not compromise survival or increase the risk of distant metastasis,” Kunkler said in the press release. “Based on these results, we believe that omission of radiation therapy after breast-conserving surgery should be an option for older patients with localized, HR-positive breast cancer who are receiving adjuvant hormone therapy and meet certain clinic-pathological criteria.”

REFERENCE
Omitting Radiation Therapy After Breast-Conserving Surgery May Not Impact 10-year Survival Rates for Older Patients With HR-Positive Breast Cancer [news release]. American Association for Cancer Research; December 9, 2020. https://www.aacr.org/about-the-aacr/newsroom/news-releases/omitting-radiation-therapy-after-breast-conserving-surgery-may-not-impact-10-year-survival-rates-for-older-patients-with-hr-positive-breast-cancer/. Accessed December 9, 2020.