SAN ANTONIO—Women 65 years of age or older who receive hormone therapy after breast-conserving surgery for hormone receptor–positive axillary node-negative breast cancer may omit whole breast radiotherapy, results of a global phase 3 study concluded at the 2013 San Antonio Breast Cancer Symposium.
“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,” said Ian Kunkler, FRCR, of the Edinburgh Cancer Research Center in the University of Edinburgh in Edinburgh, Scotland.
Although more than 50% of patients with early breast cancer present at the age of 65 years or older, evidence of the role of postoperative radiotherapy after breast-conserving surgery is sparse, he said. The aim of this study was to assess the impact on local control of the omission of radiotherapy in “low-risk” older patients.
Between April 2003 and December 2009, the PRIME II—Postoperative Radiotherapy in Minimum-Risk Elderly—study randomly assigned 1,326 patients either to receive radiotherapy (n = 658) or not receive radiotherapy (n = 668). The primary end point was ipsilateral breast tumor recurrence; secondary end points were regional recurrence, contralateral breast cancer, distant metastases, and overall survival (OS).
Mean age of the patients was similar between the two groups; 71.1 years in the no radiotherapy arm and 70.9 years in the arm receiving radiotherapy.
At a median follow-up of 5.0 years, 26 patients in the arm without radiotherapy had local recurrence, for a 5-year actuarial rate of 4.1%; in the radiotherapy arm, five patients had local recurrence, for a rate of 1.1% (95% CI: 0.1%-2.0%; P < 0.001). On multivariate analysis, the hazard ratio for local recurrence was 5.08 (95% CI: 1.95-13.24; P < 0.001).
Excluding radiotherapy did not compromise OS: the rate was 93.8% in the arm without radiotherapy (49 deaths) compared with 94.2% in the radiotherapy arm (38 deaths; P = 0.37).
“Although radiotherapy reduces ipsilateral breast tumor recurrence, the absolute reduction is very small (2.4%),” Dr. Kunkler reported. Among estrogen-receptor rich patients, the difference is 3.2% without radiotherapy versus 0.8% with radiotherapy (P = 0.003).
No significant differences were observed in regional recurrence, contralateral breast cancer, or distant metastases.
“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,” said Dr. Kunkler.
“Once a patient has had radiotherapy, they are unable to have it again on the same breast. Had these women not had radiotherapy, they would have been able to have minor surgery and radiotherapy following a recurrence,” he said. “Besides, radiotherapy carries its own health risks, particularly in the elderly, as well as the inconvenience of travel for daily treatment for 3 or 4 weeks.”
These results “are likely to lead to the consideration of omission of postoperative radiotherapy in patients meeting the eligibility criteria for the trial,” Dr. Kunkler concluded, adding they certainly warrant a discussion between physician and patient whether the modest benefit shown with radiotherapy is worth the risk.
Radiotherapy should not be omitted in patients with estrogen-receptor poor, high-grade tumors, where risk of recurrence is relatively high.
- Kunkler IH et al. S2-01. Presented at: San Antonio Breast Cancer Symposium 2013. Dec. 10-14, 2013; San Antonio.