ACCORDING to a new randomised Phase III study, males with high-risk prostate cancer could be treated with 5 rather than 8 weeks of radiotherapy. This is the first Phase III clinical trial to verify the safety and efficacy of a shorter course of radiotherapy solely for high-risk patients with the condition. Approximately 15% of males diagnosed with prostate cancer have high-risk disease, with greater chances of reoccurrence, spreading, and high mortality compared to lower-risk groups. Prostate cancer cells have radiobiological properties, which make them sensitive to changes in radiation therapy in fraction size.
The aim of the study was to maintain the prostate cancer control rates by delivering higher doses of radiation therapy per day, as well as long-term androgen deprivation therapy (ADT), but in a shorter period of time.
The Canadian multicentre trial had 329 patients who had high-risk prostate cancer, which was indicated by a higher Gleason score (8-10), Stage T3a or higher, or prostate-specific antigen above 20. The patients were randomised to either receive moderately hypofractionated radiation (68 Gy in 25 daily sessions) or conventionally fractionated prostate radiation (76 Gy in 38 daily sessions). Additionally, all patients received radiation to the pelvic lymph nodes and long-term ADT before, during, and after radiation, with a median duration of 24 months.
Upon the completion of radiation therapy 7 years later, the males who received hypofractionated or standard treatment had similar rates of recurrence and survival. The study researchers compared the results of patients who received accelerated versus standard treatment and found no differences in overall survival (81.7% versus 82%; p=0.76), prostate cancer-specific mortality (94.9% versus 96.4%; p=0.61), biochemical recurrence (87.4% versus 85.1%; p=0.69), distant metastatic recurrence (91.5% versus 91.8%; p=0.76), or disease-free survival (86.5% versus 83.4%; p=0.50). Furthermore, the side effects were similar in both groups, and no significant differences were observed in severe short- or long-term genitourinary and gastrointestinal toxicities.
“I think this trial will pave the way for patients with high-risk prostate cancer to be treated in 5 weeks instead of 8 weeks. Many of these patients are still offered 8 weeks of radiation therapy, but our trial found no benefit to the 3 extra weeks,” said lead author Tamim M. Niazi, Associate Professor of Oncology, McGill University, Montréal, Canada, and Radiation Oncologist at Jewish General Hospital, Montréal. “Survival rates and side effects, both short-term and long-term, were similar with moderately shortened radiation therapy.”
