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Canadian Researchers Find That For Some Low Risk Breast Cancers, Radiation May Not Be Needed
Michelle Milliken
Researchers at the University of British Columbia, BC Cancer, McMaster University, and Hamilton Health Services recently teamed up to gauge how surgery with only hormone therapy, and not radiation, impacted recurrence risk in breast cancer patients. They focused on the luminal A subtype, which accounts for up to 60% of breast cancer cases diagnosed each year. The findings, published in The New England Journal of Medicine, show that the risk of local recurrence within five years was low even without radiation.
Dr. Tim Whelan, lead author and professor of oncology at McMaster University, says, “This is a major advance in our treatment approach for breast cancer. With a better understanding of the molecular biology of breast cancer we can now identify women who do not need radiation.”
The research involved 500 Canadian women aged 55 and older who had undergone lumpectomies on tumors that were smaller than two centimeters and who did not have cancer in the lymph nodes under their arms. The team used a simple molecular test called Ki67 to determine a tumor’s growth rate and if it was low risk. Ki67 uses an antibody applied to tissues and a chemical reaction to see how fast tumors are growing.
Those who were determined to be low risk received just hormone therapy after their surgeries. They were given regular clinical exams and annual mammograms over the follow-up period. At the five-year mark, the researchers say the recurrence rate in this group was 2.3%. They explain that this mirrors the 1.9% risk of developing a new tumor in the other breast that had not been operated on.
The researchers say this indicates that radiation, and its cost and side effects, may not be necessary for these particular low-risk cancers. The test, which is low cost, could also be broadly used to determine risk.
Dr. Sally Smith, study co-author and radiation oncologist at BC Cancer – Victoria, says, “We are increasingly able to individualize care for patients with cancer. Adding the simple and affordable Ki67 test allows us to identify patients who can avoid the inconvenience and side effects of breast radiation. This, indirectly, helps to ensure resources are directed to patients who benefit from radiation therapy.”
The American Cancer Society says that women 65 and older may also consider a lumpectomy without radiation if their tumor was three centimeters or less and has been completely removed, if none of the lymph nodes removed had cancer, and the cancer is ER-positive or PR-positive, which means hormone therapy can be used.