Stereotactic body radiotherapy (SBRT), which delivers higher doses of radiation over a significantly shorter period of time, can be safely given to men with low- or intermediate-risk prostate cancer with similar long-term efficacy as conventional radiation therapy, a study shows.
The approach, which reduces the duration of treatment from 45 days to just four or five days, led to similar recurrence rates as other forms of radiation, “strongly suggesting that SBRT be considered a standard option for treating low-risk and intermediate-risk” patients, researchers said.
The study, “Long-term Outcomes of Stereotactic Body Radiotherapy for Low-Risk and Intermediate-Risk Prostate Cancer,” was recently published in JAMA Network Open.
“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,” lead author Amar Kishan, assistant professor of radiation oncology at the David Geffen School of Medicine at UCLA and researcher at the UCLA Jonsson Comprehensive Cancer Center, said in a press release.
“That can be very burdensome on a patient and be a huge interruption in their 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 timeframe without additional toxicity or compromising any chance of a cure,” Kishan said.
When a man receives a diagnosis of prostate cancer, multiple treatment options are available, including radiation therapy, surgery to remove the prostate and surrounding tissues, and, for those with low- or intermediate-risk disease, active surveillance.
Traditionally, men receive radiation therapy in the form of definitive external beam radiotherapy (EBRT), which consists of small doses of radiation given every day for eight or nine weeks. But studies suggest that prostate cancer is sensitive to higher doses of radiation given in shorter periods of time.
Several clinical trials have followed patients receiving SBRT for up to five years, reporting low recurrence rates, reduced costs of treatment due to fewer treatments involved, and less regret about undergoing treatment. But researchers have raised concerns about the long-term toxic effects of the approach.
To address that, UCLA researchers examined data from 2,142 men with low- or intermediate-risk prostate cancer, treated with stereotactic body radiotherapy across multiple institutions between 2000 and 2012.
Participants had a mean age of 68 years and were followed for a median of 6.9 years after treatment. Most of these men (55.3%) had low-risk disease, 32.3% had a less aggressive type of intermediate-risk disease, and 12.4% had an unfavorable intermediate-risk disease.
Overall, the rates of biochemical recurrence — deemed as a rise in PSA levels — at seven years were 4.9% for low-risk patients, 8.6% for favorable intermediate-risk patients, and 14.9% for patients with unfavorable intermediate-risk disease.
To confirm the effectiveness of the approach, researchers gathered data from other trials assessing the biochemical relapse rates with other radiation therapy approaches. They found that these rates were identical, and perhaps even lower, to those seen with more conventional forms of radiation.
Severe toxic events were rare, both immediately after treatment and in the long term, with only 2.4% and 0.4% of patients experiencing late severe adverse events in their gastrointestinal and genitourinary tracts within three years of treatment.
During the study, no patients died from prostate cancer.
“What is remarkable about this very large study is how favorably stereotactic body radiotherapy compares to all other forms of radiation treatments, both in terms of effectiveness and side effects,” said senior author Christopher King, professor of radiation oncology and scientist at the UCLA cancer center. “With such long-term follow-up data, we can now offer this approach to patients with full confidence.”
Kishan said, “We not only confirm that this method is both safe and effective, but we provide significant evidence that this could be a viable treatment option for men with low and intermediate risk of prostate cancer.”