Miami, FL—Delivering higher doses of external-beam radiation over a shorter period (hypofractionated radiation) was as effective as conventional radiation in preventing treatment failure in men with intermediate- to high-risk prostate cancer. The hypofractionated regimen shortened treatment time by 2.5 weeks compared with conventional radiation. However, the frequency of grade 2 or higher genitourinary (GU) adverse events, particularly urinary incontinence, was much higher with the hypofractionated regimen in a phase 3 trial presented at the meeting. The study hypothesis was that hypofractionation would be superior to conventional radiotherapy in avoiding biochemical failure and would not cause greater toxicity, but the results failed to show this. Lead investigator Alan Pollack, MD, Chair of Radiation Oncology, University of Miami, FL, said that hypofractionated radiation was an option for men with intermediate- to high-risk prostate cancer, but there may be a trade-off between shorter treatment time and an increase in GU adverse events with this regimen. “Hypofractionation is more convenient for patients and less costly,” Dr Pollack said. The study population included 303 men with intermediate (66%)- or highrisk (33%) prostate cancer. Two thirds had intermediate-risk cancer and one third had high-risk cancer. Baseline characteristics were similar for both groups. Treatment failure was defined as a prostate-specific antigen rise of ?2 ng/mL from the lowest value. The 5- year cumulative incidence of treatment failure was 13.9% in the hypofractionation group versus 14.4% in the conventional radiotherapy group. Overall, biochemical failure was reported for 61 patients, with no significant difference in failure rate between the 2 arms. The 5-year rates of local regional failure or distant metastasis were similar for both arms: 1.3% for the hypofractionation group and 1% for the conventional radiotherapy group. Hypofractionation was associated with a higher rate of grade 2 and higher GU toxicity: 18.3% for hypofractionation versus 8.3% for conventional radiotherapy. Urinary incontinence was the most frequent GU adverse event, and the rate of late urinary problems was more favorable in both treatment arms compared with previous studies. The long-term rates of gastrointestinal adverse events and erectile dysfunction were identical for the 2 arms. In a post hoc analysis, the American Urological Society (AUA) symptom score for pretreatment urinary function was the strongest predictor of GU adverse events in the hypofractionation group. Overall, the median AUA score was 5.
