A new UCLA-led study shows that men with low- or intermediate-risk prostate cancer can safely undergo higher doses of radiation over a significantly shorter period of time and still have the same successful outcomes as from a much longer course of treatment. This type of radiation, known as stereotactic body radiotherapy, is a form of external beam radiation therapy and reduces the duration of treatment from 45 days to four-to-five days. The approach has been in use since 2000 but has not yet been widely adopted because of concerns over how safe and effective this approach would be in the long term.
Figure shows rates of clinically significant urinary side effects, such as bleeding or obstruction (top), and clinically significant gastrointestinal side effects, such as bleeding or diarrhea (bottom), grouped by various treatment modalities. Rates of toxicity from stereotactic body radiotherapy are indicated at the bottom of each graph and appear to compare favorably with rates associated with other older and more commonly used techniques.
Graphic: Courtesy of Dr. Amar Kishan
“Most men with low- or intermediate-risk prostate cancer undergo conventional radiation, which requires them to come in daily for treatment and takes an average of nine weeks to complete,” says Amar Kishan, MD (RES ’17), assistant professor of radiation oncology and a researcher at the UCLA Jonsson Comprehensive Cancer Center. “That can be very burdensome on a patient and a huge interruption in his life. With the improvements being made to modern technology, we’ve found that using stereotactic body radiotherapy, which has a higher dose of radiation, can safely and effectively be done in a much shorter time frame without additional toxicity or compromising any chance of a cure.”
Men in the study were followed for a median of 6.9 years. Fifty-three percent of the men had low-risk disease, 32 percent had less aggressive intermediate-risk disease and 12 percent had a more aggressive form of intermediate-risk disease. The recurrence rate for men with low-risk disease was 4.5 percent, the recurrence rate for the less aggressive intermediate-risk was 8.6 percent and the recurrence rate for the more aggressive intermediate-risk group was 14.9 percent. Overall, the recurrence rate for intermediate-risk disease was 10.2 percent. These are essentially identical to rates following more conventional forms of radiation, which are about 4-to-5 percent for low-risk disease and 10-to-15 percent for intermediate-risk disease.
Researchers previously have found that stereotactic body radiation therapy was more cost effective because of the fewer treatments involved. Other research also has suggested psychological benefits, such as less regret about undergoing treatment. The current study now provides long-term data regarding the safety and clinical efficacy of this approach.
Dr. Kishan says the data show that the majority of the men followed are free of prostate cancer seven years after treatment. He added that there was no evidence that this therapy caused worse toxicity in the long term.
— Denise Heady
“Long-term Outcomes of Stereotactic Body Radiotherapy for Low-risk and Intermediate-risk Prostate Cancer,” JAMA Network Open, February 8, 2019
