ASTRO: High-dose, shorter duration RT effective in treating prostate cancer

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Hypofractionation regimens of radiation therapy, which deliver higher doses of radiation per day, but in fewer days, are as effective in decreasing intermediate to high-risk prostate cancer from returning as conventional radiation therapy at five years post-treatment, according to a randomized trial to be presented at the 53 rd Annual Meeting of the American Society for Radiation Oncology (ASTRO) in Miami, Oct. 2-6.

Alan Pollack, MD, of the Miller School of Medicine at the University of Miami, and colleagues were looking for a way to increase radiation doses to better control tumors without increasing side effects.

“We hypothesized that dose escalation could be achieved with hypofractionation without increasing toxicity based on data that relate to how best to apply hypofractionation and biologic principles that have been worked out,” Pollack said in a news briefing on Sept. 26.

Prior research had indicated that tumor cells would be killed more effectively using hypofractionation, while not increasing damage to the surrounding normal tissues of the rectum, penile structures and bladder.

In this particular trial, the researchers utilized intensity modulated radiotherapy (IMRT), which further limits dose to normal tissues.

A total of 303 men with intermediate to high-risk prostate cancer were randomized to receive either hypofractionated IMRT or conventional IMRT between 2002 and 2006. Patients were followed for five years and cancer recurrence was monitored by checking prostate specific antigen (PSA) levels.

The hypofractionation IMRT approach used in the trial was given over a shorter period of time than conventional IMRT, but because of the higher daily dose, overall it was estimated to be the equivalent of four extra treatments using conventional approaches.

Patients in the conventional IMRT arm had better outcomes than anticipated, with observed tumor control rates nearly identical to the patients receiving hypofractionated IMRT. The major benefit of hypofractionation was that it achieved comparable results in two and a half fewer weeks of treatment.

Side effects were comparable between the two approaches in most regards, and were relatively low for both methods. Identical long-term rates of rectal reactions and erectile dysfunction were observed.

There was, however, an increase in the rate of urinary side effects, particularly loss of bladder control, in the patients receiving hypofractionated IMRT.

“There may be a tradeoff with this particular regimen. I think we’re learning exactly how to apply hypofractionation, what the limits are,” said Pollack, who added that despite the moderate urinary side effects, the trial showed the technique is very effective.

Hypofractionation is gaining momentum in the treatment of many types of cancers, according to Pollack, who concluded that the results demonstrated that it is possible to effectively treat prostate cancer in a shorter period of time with acceptable side effects.