Wednesday, December 16, 2020 Postmenopausal women with hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer that has spread to a limited number of lymph nodes, and whose recurrence risk is relatively low, do not benefit from chemotherapy when it is added to hormone therapy, according to initial results from the MAC15 RxPONDER trial presented at the 2020 San Antonio Breast Cancer Symposium. These findings may save tens of thousands of postmenopausal women each year the time, money, and harmful side effects that come with chemotherapy infusions. This is the first evidence in a randomized phase III trial that postmenopausal women with HR-positive, HER2-negative breast cancer that has spread to one to three lymph nodes can safely forgo chemotherapy if their recurrence score on a genomic tumor tissue test is 25 or less. The trial also demonstrated, after a median of five years of follow-up, that premenopausal women with the same disease characteristics benefited from chemotherapy. “The five-year data from the MAC15 RxPONDER study indicate that post-menopausal women with one to three node-positive estrogen receptor positive, HER2 negative disease and a Recurrence Score result of 25 or less can be spared chemotherapy,” said Dr. Stephen Chia, the CCTG Co-Chair of the Breast Disease Site, Head of the University of British Columbia Division of Medical Oncology and Oncologist, UBC Cancer. “For the 25% of Canadian women with hormone receptor positive, HER2 negative breast cancer who have one to three lymph nodes involved and a Recurrence Score result, these practice-changing data provide a new level of confidence to physicians and their patients as they make these critical treatment decisions.” RxPONDER follows the ground-breaking TAILORx study, which showed that postmenopausal women with lymph node-negative, HR-positive, HER2-negative breast cancer and recurrence scores of 25 or less on a genomic tumor tissue test saw no benefit from the addition of chemotherapy to hormone therapy compared with hormone therapy alone. These results, however, left open the question of the most effective way to treat women diagnosed with more advanced breast cancer that has spread to the lymph nodes. “The decision to recommend adjuvant chemotherapy to women with breast cancer is a balance between the survival benefits and potential life altering side effects of treatment. The MAC15 RxPONDER trial is an important step forward, demonstrating that not all women with ER positive and HER 2 negative, node positive breast cancer require chemotherapy,” says Dr. Bindi Dhesy-Thind, the other CCTG study lead and Oncologist at Hamilton Health Sciences. “The practice changing results of this landmark trial will pave the way for further de-escalation of treatment in this favourable prognosis group.” RxPONDER was an international effort, conducted at 632 sites in nine countries — the United States, Canada, Mexico, Colombia, Ireland, France, Spain, Korea, and Saudi Arabia. “The Canadian Cancer Trials Group under the leadership of Dr. Chia and Dr. Dhesy-Thind, participated in the RxPONDER trial and randomized 328 women to the study or 6.5% of the overall accrual. Women were recruited from across Canada and their generosity of participation has contributed to this exciting study results,” says CCTG Senior Investigator Dr. Lois Shepherd. “In Canada we had 24 sites participate testing 734 women - 328 of those were randomized.” Find out more here.
