A shorter course of radiation treatment that delivers higher doses of radiation per day in fewer days (hypofractionation) is as effective in decreasing intermediate to high-risk prostate cancer from returning as conventional radiation therapy at five years after treatment, according to a randomized trial presented at the plenary session, October 3, 2011, at the 53rdAnnual Meeting of the American Society for Radiation Oncology (ASTRO).
"This long-term study confirms that hypofractionated radiation that shortens treatment by about two and a half weeks is a practical approach to effectively controlling prostate cancer, as compared to the more standard treatment for men with intermediate to high-risk prostate cancer," Alan Pollack, MD, chairman of radiation oncology at the University of Miami Miller School of Medicine in Miami, said.
The strategy to compress treatment schedules using hypofractionation is based on years of studies indicating that there could be a radiobiologic advantage to this approach. Prior research has indicated that tumor cells would be killed to a greater degree with hypofractionation than the potentially damaging effects on the surrounding normal tissues, namely the rectum, penile structures affecting erections and bladder. Another newer approach to hypofractionation incorporated into this trial is the use of intensity modulated radiotherapy (IMRT), which further limits dose to the normal tissues. IMRT has proven value in limiting side effects in the treatment of prostate cancer with external beam radiotherapy.
The study involved 303 men with intermediate to high-risk prostate cancer who were randomized to receive either hypofractionated IMRT or conventionally fractionated IMRT between 2002 and 2006. The high risk patients also received a form of hormone therapy for two years. The patients were followed for over five years to find out if their cancer returned by monitoring prostate specific antigen (PSA), a blood test and established indicator of prostate cancer recurrence when increasing levels are seen.
Dr. Pollack said, "we are still learning how best to apply hypofractionation and the results in this trial show that the technique is very effective."
The hypofractionation approach used was given in a shorter period of time with higher doses per day and was expected to be equivalent to four extra treatments using conventional fractionation. While the hypofractionation treatment was hypothesized to be superior, the same tumor control rates were observed. The conventionally fractionated patients had better outcomes than expected. The benefit of the hypofractionation method used was that comparable results were achieved in two and a half fewer weeks of treatment.
In terms of side effects, the rates were relatively low for both methods. There were identical long-term rates of bowel/rectal reactions and the frequency of unsatisfactory erections. There was, however, significantly higher bladder control in the conventionally fractionated patients.
"Late urinary symptoms were higher with hypofractionation but were low overall, particularly when the incidence of persistent urinary symptoms (<10 percent at five years) was analyzed, rather than just as an isolated event," Dr. Pollack said. "Hypofractionation is rapidly gaining momentum for many types of cancers. The results presented here bring us much closer to effectively treating prostate cancer in a shorter period of time, with acceptable side effects."
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