Preventing Impotence from Prostate Radiation

Radiation therapy for prostate cancer is successful for men with prostate cancer, however, up to 90% will develop impotence after the therapy. A new study indicates that this side effect may be avoided if both magnetic resonance imaging (MRI) and computed tomography (CT) are utilized to strategize precisely how and where radiation will be deployed, rather than just CT.

Earlier studies have suggested that radiation on the prostate causes impotence by injuring the structures that control blood supply to the penis. Consequently, radiotherapy that avoids these structures could possibly preserve sexual function. According to researchers at the University of Michigan (UMich, Ann Arbor, MI, USA; www.umich.edu), with conventional CT therapy it is frequently believed that the distance between these major structures and the prostate is 1.5 cm; however, using this approximation on all patients is going to result in treating more tissue than is needed.

The UMich investigators used a combination of CT and MRI scanning to determine the precise distance from the prostate to the blood-containing structures in 25 men with prostate cancer. Even though the median distance--1.45 cm--was close enough to that used with CT-based therapy planning, the values differed extensively from 0-7-2.1 cm. The precise calculation of the distance permitted the group to be able to more precisely pinpoint radiotherapy to where it is needed to greatly reduce the dose to the vital erection structures.

Additional research is still needed to determine if combined CT and MRI planning of radiation therapy does in fact prevent impotence, according to the investigators, who published their results in the January 2005 issue of the International Journal of Radiation Oncology Biology Physics.




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