Women with early-stage breast cancer who receive large doses of radiation once a week for five weeks will experience the same long-term side effects as women who undergo conventional radiation therapy, according to a ten-year study presented Oct. 21 at the 2018 American Society for Radiation Oncology (ASTRO) annual meeting in San Antonio, Texas.
Findings from the multi-institutional research could help doctors and patients better discuss risks and benefits of various courses of radiation therapy and improve shared-decision making overall.
“This study says it’s possible to find a regimen that would allow early-stage breast cancer patients to be treated only once a week over five weeks rather than daily over the same time period,” lead author Murray Brunt, MD, a professor of clinical oncology at University Hospitals of North Midlands and Keele University in the U.K., said in a prepared statement. “Findings should help doctors discuss risks and benefits with their patients for various courses of radiation therapy and inform shared decision-making between physicians and patients.”
The study is part of a long-term report of the FAST (FASTer Radiotherapy for breast cancer patients) trial designed to assess changes in healthy breast tissue following conventional radiation treatment compared with two shorter regimens that delivered higher doses of radiation in fewer sessions, according to the release. This trial—led by the Institute of Cancer Research in London—involved a total of 915 women diagnosed with early-stage breast cancer at 18 centers across the U.K. from 2004 to 2007.
The current study confirms the results of the initial trial published in 2011, which demonstrated that a once a week, hypofractionated therapy had the same low-normal tissue effects as conventional radiation therapy after two years of treatment. Moreover, the current study showed that these similarities were present for an additional eight years.
For the current study, patients were randomly assigned to one of three whole-breast radiation therapy regimens following breast-conserving surgery: conventional treatment with 50 Gray (Gy) of radiation delivered in 25 daily, 2 Gy fractions over five weeks; or hypofractionated treatment with one of two doses: 30 Gy delivered in five, once-weekly fractions of 6 Gy each, or 28.5 Gy delivered in five, once-weekly fractions of 5.7 Gy each.
Overall, moderate and severe long-term effects to normal tissue from radiation therapy were low for all groups after each treatment, according to the researchers. Additionally, minor changes or no changes in normal tissue were found in 88 and 86 percent of women after five and 10 years, respectively.
The researchers also noted that late normal tissue effects were not statistically different between the conventional group and the group that received five weekly treatments at 5.7 Gy each. Patients who received five weekly treatment sat 6 Gy, however, were more likely to experience breast shrinkage, hardness, fluid build-up or spider veins.
Continuing their work, Brunt and colleagues are investigating radiation therapy with five fractions delivered over five consecutive days.
“As a next step, we want to investigate shortening the radiation therapy schedule to one week,” Brunt said. “A schedule like this would have significant clinical and practical implications, such as allowing radiation therapy to be integrated more closely with surgery and other therapies.”