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PUBLIC RELEASE DATE:
11-Dec-2013

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Contact: Jeremy Moore
jeremy.moore@aacr.org
215-446-7109
American Association for Cancer Research

Avoiding radiotherapy is an option for some older patients with breast cancer

SAN ANTONIO Omission of radiotherapy is a reasonable option for women age 65 or older who receive hormone therapy after breast-conserving surgery for hormone receptor-positive, axillary node-negative breast cancer, according to results of the PRIME 2 trial presented here at the 2013 San Antonio Breast Cancer Symposium, held Dec. 10-14.

"Radiotherapy has been known to reduce the risk of breast cancer recurrence three- to fourfold. However, what our trial has shown is that although this is still the case, the proportion of women who will actually have a recurrence without radiotherapy is very small (less than 5 percent), five years after treatment," said Ian Kunkler, F.R.C.R., professor of clinical oncology at the Edinburgh Cancer Research Center in the University of Edinburgh. "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.

"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 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 explained. "Besides, radiotherapy carries its own health risks, particularly in the elderly, as well as the inconvenience of travel for daily treatment for three or four weeks.

"Allowing us to defer radiotherapy in this group of patients until a recurrence occurs will be of benefit to the patient and to the health service," said Kunkler.

PRIME 2 is an international, phase III, randomized, controlled trial that set out to address the question of whether whole-breast radiotherapy can be omitted in carefully defined groups of older patients receiving appropriate therapy. The primary endpoint of this trial is recurrence of breast cancer in the same breast, known as ipsilateral breast tumor recurrence (IBTR).

The investigators found that at five years, 1.3 percent of patients who received radiotherapy had IBTR, and 4.1 percent of patients who did not receive radiotherapy had IBTR.

Between 2003 and 2009, 1,326 patients were enrolled in the trial; 658 patients were randomly assigned to receive radiotherapy and 668 did not receive radiotherapy. All participants were age 65 or older; had hormone-positive, low-grade breast cancer; did not have the disease in lymph nodes adjacent to the breast (axillary node-negative); did not have metastasis; had cancer-free breast tissue margins where tumor was surgically removed; and received hormone therapy.

The investigators found that at five years, between patients who received radiotherapy and those who did not, there was no significant difference in overall survival (97 percent vs. 96.4 percent); regional recurrence (0.5 percent vs. 0.8 percent); or breast cancer in the opposite breast (0.5 percent vs. 0.7 percent). The difference in breast cancer-free survival between those receiving and not receiving radiotherapy (98.5 percent vs. 96.4 percent), however, was statistically significant.

"Our results are likely to lead to the consideration of omission of postoperative radiotherapy in patients meeting the eligibility criteria for the trial," Kunkler said.

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This research will be presented at the 2013 San Antonio Breast Cancer Symposium Wednesday, Dec. 11, 7:30 a.m. CT, during a press conference hosted by C. Kent Osborne, M.D., director of the Dan L. Duncan Cancer Center and director of the Lester and Sue Smith Breast Center at Baylor College of Medicine. Press conferences will be held in Room 217D of the Henry B. Gonzalez Convention Center, San Antonio, Texas.

Reporters who cannot attend in person can call into the press conferences using the following information:

To interview Ian Kunkler, contact Eleanor Cowie at eleanor.cowie@ed.ac.uk or +44-0-131-650-6382. For other inquiries, contact Jeremy Moore at jeremy.moore@aacr.org or 215-446-7109.

This study was funded by the Chief Scientist's Office for Scotland. Kunkler declares no conflicts of interest.

The mission of the 2013 San Antonio Breast Cancer Symposium is to produce a unique and comprehensive scientific meeting that encompasses the full spectrum of breast cancer research, facilitating the rapid translation of new knowledge into better care for patients with breast cancer. The Cancer Therapy & Research Center (CTRC) at The University of Texas Health Science Center at San Antonio, the American Association for Cancer Research (AACR), and Baylor College of Medicine are joint sponsors of the San Antonio Breast Cancer Symposium. This collaboration utilizes the clinical strengths of the CTRC and Baylor and the AACR's scientific prestige in basic, translational, and clinical cancer research to expedite the delivery of the latest scientific advances to the clinic. For more information about the symposium, please visit http://www.sabcs.org.

Publication Number: S2-01

Presenter: Ian Kunkler, F.R.C.R.

Title: The PRIME 2 trial: Wide local excision and adjuvant hormonal therapy postoperative whole breast irradiation in women ≥65 years with early breast cancer managed by breast conservation

Authors: Ian H Kunkler1, Linda W Williams1, Wilma Jack2, Peter Canney3, Robin J Prescott1 and Michael J Dixon1. 1University of Edinburgh, Edinburgh, Midlothian, United Kingdom; 2Edinburgh Cancer Centre, Edinburgh, Midlothian, United Kingdom and 3Beatson Oncology Centre, Glasgow, West of Scotland, United Kingdom.

Background: Local recurrence rates after breast conserving surgery (BCS) are falling because of increasing use of effective systemic therapy. The question of whether whole breast radiotherapy (WBRT) can be omitted in carefully defined groups of older patients receiving appropriate systemic therapy has not been addressed. PRIME II is an International phase III RCT addressing this question

Methods: Between April 2003 and December 2009, 1326 patients were randomised to receive (n=658) or nor receive (n=668) radiotherapy (RT). Eligibility criteria were age=/>65 years, T1-2 (up to 3cm), N0, M0, hormone receptor positive, clear excision margins (minimum 1mm), axillary node negative women in receipt of adjuvant hormone therapy. Patients could have Grade 3 tumours or lympho-vascular invasion but not both. An accrual of 1300 was planned to detect a difference based on estimates of local recurrence of 2% in RT group and 5% in no RT arm at 5 years, with 80% power and 5% significance. The primary endpoint was ipsilateral breast tumour recurrence (IBTR). Secondary endpoints were regional recurrence, contralateral breast cancer, distant metastases and overall survival (OS). Median follow up is 4.8 years.

Results: IBTR at 5 years was 2.7% (95% CI 1.4, 4.0) without RT, and 0.6% (95% CI 0, 1.3) with RT. The hazard ratio for IBTR in those IBTR receiving radiotherapy was 4.3 (95% CI 1.4, 12.7) (p=0.004). Overall survival at 5 years was 96.4% (95% CI 94.7, 97.9) without RT and 97.0% (95% CI 95.6, 98.4) with RT, (p=0.25). No significant differences in regional recurrence (0.8% no RT vs 0.5% RT), contralateral breast cancer (0.7% no RT vs 0.5% RT), nor distant metastases (0.5% no RT vs 0.3% RT) were seen. Breast cancer-free survival was 96.4% (95% CI 94.9, 97.9) for no RT and 98.5% (95% CI 97.5, 99.6) for those receiving RT (p=0.03): this difference was due to the greater IBTR in no RT group. The majority of deaths were not linked to breast cancer (32 no RT vs 24 RT from a total of 76 deaths), with no influence of omission of RT (p=0.3).

Conclusions: The PRIME2 randomised international Trial has shown that: Omission of RT in women age=/>65 years of age with pN0, hormone receptor positive breast cancer receiving endocrine therapy results in only a 2.7% 5 year IBTR. Although RT reduces IBTR significantly, the absolute reduction in this study is very small. RT does not reduce the rate of regional recurrence, distant metastases or overall survival. Early results only, 5 year median follow up results to follow in November.



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