"We found that omitting postoperative radiation therapy did not compromise survival or increase the risk of distant metastasis," Dr. Ian Kunkler of the University of Edinburgh said in a news release from the 2020 San Antonio Breast Cancer Symposium where he presented the data.
Based on these results, omission of postoperative radiation after breast-conserving surgery is a "reasonable option" for older women with localized, HR-positive breast cancer who are receiving adjuvant hormone therapy and meet certain clinico-pathological criteria, Dr. Kunkler told the conference.
The PRIME II study enrolled 1,326 women aged 65 and older with localized, HR-positive, axillary node-negative breast cancer up to 3 cm (T1-2) who had undergone breast-conserving surgery, and were on adjuvant hormone therapy. They were randomly allocated to either receive or not receive whole-breast RT after surgery.
After a median follow-up of five years, rates of local breast-tumor recurrence were higher in women who did not receive RT relative to those who did (4.1% vs. 1.3%) but there was no significant difference in overall survival, distant metastases, or new breast cancers. The five-year data were reported in The Lancet in 2015 (https://bit.ly/37NngdF).
The 10-year data continue to show a higher rate of local recurrence in women who did not receive RT (9.8% vs. 0.9%), but with no significant between-group differences in distant metastasis (1.4% vs. 3.6%), contralateral breast cancer (1.0% vs. 2.2%), and overall survival (80.4% vs. 81.0%). Most deaths were not due to breast cancer.
Weighing in on the results, Dr. Stephanie Bernik, chief of the breast service at Mount Sinai West and associate professor of surgery at the Icahn School of Medicine at Mount Sinai in New York City, urged caution in interpreting the results, noting that the recurrence rates without radiation are not something to take lightly.
The recurrence rate "wasn't quite 10%, but it was significantly higher and those patients have to deal with cancer again, which is not insignificant. Recurrences lead to more treatments, probably more aggressive surgeries and chemotherapy, potentially," Dr. Bernik, who was not involved in the study, told Reuters Health by email.
"For someone who is healthy, I don't really see the downside of undergoing a few weeks of radiation when you are definitely decreasing the risk of recurrence. I guess it should be the woman's choice," said Dr. Bernik.
"Either way, knowledge is power and this is important information because you can tell a patient that this is the recurrence rate with or without radiation, but this study is certainly not going to make me recommend not radiating people. That's the wrong message," she added.
SOURCE: https://bit.ly/33UKdKv 2020 San Antonio Breast Cancer Symposium, presented December 9, 2020.
By Megan Brooks
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