ScienceDaily (Oct. 31, 2007) — Recent advances in the delivery of radiation therapy for prostate cancer are fueling a new trend of providing higher radiation doses over shorter periods of time. But does the daily increase in radiation lead to more sexual dysfunction than the conventional dose? New research by physicians at Fox Chase Cancer Center says it does not. 

IMRT, or intensity-modulated radiation therapy, is a technique for delivering radiation that more precisely targets the tumor. Because of this precision, physicians can increase the dose of radiation, which is shown to cure more prostate cancers, without increasing side effects of radiation such as rectal bleeding, cramps or diarrhea.

"Sexual dysfunction can be a result of radiation treatment for prostate cancer," said Mark Buyyounouski, M.D., attending physician in the radiation oncology department at Fox Chase Cancer Center and lead author of this study. "IMRT is revolutionizing how we treat men with prostate cancer because it improves our ability to avoid normal tissue. As a result, more radiation dose can be delivered to the prostate by increasing the amount of radiation each day. Increasing the radiation used each day is particularly attractive because it also shortens the treatment time by several days.

"We need to make sure there's a balance between risk and benefit, and sexual function is a major consideration. Fortunately, this study shows no decrease in sexual function from the higher doses of radiation."

For the study, 155 men with intermediate- to high-risk prostate cancer were prospectively randomized to receive 2 Gy in 38 fractions or sessions (seven weeks, three days), totaling 76 Gy, or a short course of 2.7 Gy in 26 fractions (five weeks, one day), totaling 70.2 Gy. IMRT planning was used in both arms. Men who received androgen-deprivation therapy were excluded from the analysis. Sexual function was reported by patients using questionnaires before treatment and at six, 12 and 24 months after treatment.

Seventy-seven men received the seven and a half week treatment and 78 men received the shorter regimen with higher daily dose. There was no significant difference in sexual function scores between the two groups at six, 12 months or 24 months following treatment. Older age and poorer sexual function prior to treatment were related to a decline in sexual function after treatment. The shorter arm was not associated with erection quality or frequency at two years.

"There continued to be no difference in sexual function between the two groups at six, 12 or 24 months" concluded Buyyounouski. "Men who had low sexual function before treatment were most likely to have a decline in sexual function after treatment.. "Increasing radiation dose with hypofractionation and IMRT does not appear to increase that risk."

This research was presented at the American Society for Therapeutic Radiology and Oncology's 49th Annual Meeting in Los Angeles.