A single, targeted high dose of radiation delivered before other treatments could completely eradicate tumours in most women with early-stage, operable hormone-positive breast cancer, according to a study led by UT Southwestern Medical Center researchers. The findings, published in JAMA Network Open, could shift the paradigm for patients with the most common form of breast cancer, who typically undergo surgery before a regimen of radiation therapy.
“This is a major advance in the field,” said study leader Asal Rahimi, MD, Professor of Radiation Oncology. “This treatment protocol provides patients a significant time savings, spares a lot of their tissue from irradiation, and allows them to still undergo any type of oncoplastic surgery they may choose, all while very effectively treating their disease.”
Like patients with other forms of cancer, those with breast cancer are typically treated with a combination of surgery to remove tumours, medications such as hormone blockers, chemotherapy, and radiation, often in that order. In addition, many patients choose to have breast reconstructive surgeries before radiation treatment.
Having targeted radiation prior to surgery has several benefits, including a more than 100-fold smaller volume of tissue being irradiated compared with whole breast radiation; one day of radiation compared with up to 6.5 weeks of radiation, creating a huge time savings for patients; and more options for patients seeking reconstructive surgery, explained Dr Rahimi.
Early-stage, hormone-positive breast cancer accounts for 60–75% of all breast cancers. Seeking a more time-efficient way to treat these patients, Dr Rahimi and her colleagues tested a strategy in which 44 patients started treatment with a single dose of targeted radiation. While typical radiation therapy protocols call for 1.8–2.67Gy per day for 16 to 33 days, the researchers divided the study participants into three groups and gave each patient a single dose of 30, 34, or 38Gy. The volunteers then went on hormone-blocking drugs and waited a median of 9.8 months until they underwent surgery to remove any residual tumour tissue.
In 72% of study participants, the surgeons found no residual tumor left, indicating that patients had a “pathological complete response.” An additional 21% of patients had a “near complete response,” meaning that their cancer was more than 90% eliminated.
Further analysis showed that time to surgery was the best predictor of response. The longer patients waited to undergo surgery, the more likely their tumours were to disappear, regardless of the radiation dose or tumour size. These results were probably due to the time it takes cells to die or be removed by the immune system after radiation therapy, Dr Rahimi explained.
This new treatment protocol could hold significant advantages over the current gold standard, said Marilyn Leitch, MD, Professor of Surgery. For example, being able to wait to schedule surgery will allow patients to plan for the disruption it brings to their lives. The radiation course lasts a single day rather than weeks. Plus, in the future, this new approach may eliminate the need for surgery in some patients.
“Much of the current research in breast cancer is looking at ways to reduce the extent of surgery, radiation, and/or medical therapy that is required to completely treat early-stage breast cancer. It is very exciting to be part of innovative research that can improve the quality of life of our cancer patients and minimize the extent of treatment they require,” Dr Leitch said.
The research team is currently enrolling patients in a phase two clinical trial. “If the results mirror the ones from this study, an initial targeted dose of radiation could become a new treatment option for patients with small, early-stage, hormone-positive breast cancer,” Dr Leitch said.
Source: UT Southwestern Medical Center
