NEW YORK (Reuters Health) – Some older women with breast cancer may be able to skip postoperative radiotherapy, according to results of the PRIME 2 study presented December 11 at the San Antonio Breast Cancer Symposium.
Radiotherapy after breast conserving surgery is the standard of care regardless of risk factors, including age. “But older patients now represent an increasing proportion of patients that we see in the clinic, over 50%, and they often have a relatively benign natural history and radiotherapy may represent overtreatment,” said Dr. Ian Kunkler of the Edinburgh Cancer Research Center in Scotland, at a media briefing.
In addition, there is “relatively sparse level 1 evidence” in this older age group for postoperative radiotherapy after breast conserving surgery, he noted.
What the PRIME 2 study has shown, Dr. Kunkler said, is that the proportion of older “minimum risk” women who will actually have a recurrence without radiotherapy is “very small, less than 5%, five years after treatment.”
Between 2003 and 2009, researchers enrolled 1,326 women, aged at least 65, with T1-2 (up to 3 cm), N0, M0, hormone receptor positive, axillary node negative, unilateral invasive breast cancer and clear excision margins (minimum 1 mm) after breast conserving surgery.
All received preoperative and postoperative endocrine therapy.
In addition, 658 women received radiotherapy and 668 did not. The primary endpoint is ipsilateral breast tumor recurrence (IBTR).
At five years, six women (1.3%) who received radiotherapy had IBTR, as did 26 women (4.1%) who did not receive radiotherapy (p=0.02).
“What this study shows is that for every 100 women (from our selected population) treated with radiotherapy, one will have a recurrence anyway, four will have a recurrence prevented, but 95 will have had unnecessary treatment,” Dr. Kunkler said in a statement from the conference.
“We have identified a subgroup of older patients at sufficiently low risk of recurrence for whom omission of postoperative radiotherapy after breast-conserving surgery and adjuvant endocrine therapy is a reasonable option,” he added.
The study also showed that omitting radiotherapy after breast conserving surgery in this select group “does not compromise overall survival,” Dr. Kunkler said. Overall survival at five years was 97% with radiotherapy and 96% without. There was also difference in regional recurrence (0.5% vs. 0.8%) or breast cancer in the opposite breast (0.5% vs. 0.7%).
“Our results are likely to lead to the consideration of omission of postoperative radiotherapy in patients meeting the eligibility criteria for this trial,” Dr. Kunkler said.
This study addresses the concept that more is not better, said Dr. C. Kent Osborne, director of the Dan L. Duncan Cancer Center and director of the Lester and Sue Smith Breast Center at Baylor College of Medicine in Houston, who moderated the press briefing.
He explained, “When I was in my training 40 years ago we were in the era of more is better, that is, everybody thought that if you gave more treatment, more surgery, more radiation, more chemotherapy, that would be better. It’s turning out now that we’ve evolved over the last three decades (and) that is not the case. Now we are in a transition between a lot of the things we’ve done in the past and a lot of the things that we are going to be doing in the future.”
This study was funded by the Chief Scientist’s Office for Scotland. Dr. Kunkler and Dr. Osborne have no conflicts of interest.