Radiation therapy

Content written by John P. Mulhall, MD

Radiation therapy is used in the treatment of many cancers and has been used very successfully to cure men and women of their cancers. Radiation to organs in the pelvis in both men and women may be associated with sexual problems. The most common reasons for radiation to the pelvis in men include prostate cancer, bladder cancer, penile cancer and rectal cancer. This form of therapy involves the delivery of varied forms of rays to the organs involved by cancer. Since its introduction in the 1950s there have been tremendous advances in the technology used to ensure that tissues other than the cancer are not exposed to radiation. Saying that, it is well appreciated that even with modern radiation therapy delivery methods, a small yet significant amount of radiation will go to surrounding structures. For example, in the treatment of prostate cancer, while the radiation beam is directed towards the prostate a zone of between ½-1 cm around the prostate will also be targeted and radiation will also unfortunately go beyond this region to the bladder, rectum and the penis. It has been estimated using even modern treatment called IMRT delivers approximately one quarter of the total radiation dose to the very back portion of the penis. Of note the penis sits approximately 1-2 cm from the tip of the prostate so it is easy to understand how some radiation exposure may occur to the penis. Radiation in the pelvis is well known to cause erectile dysfunction. The magnitude of its negative effect on erectile function is related to the dose as well as the patients pre-radiation erectile function, his age and comorbidity status (whether he has high blood pressure, high cholesterol, diabetes and coronary artery disease for example). Radiation has a negative effect on erectile function in three ways. Radiation has a profound negative impact upon blood vessels, in particular the lining of these blood vessels known as the a endothelium. Secondly erectile tissue damage, the muscle present within the center of the erection chambers known as the corpora cavernosa, is exquisitely sensitive to radiation and can undergo direct damage when exposed to it. Thirdly, radiation has a negative effect on the structure and function of the erection nerves that travel very close to the prostate. While radical prostatectomy is classically associated with a very abrupt change in erectile function, radiation therapy on the other hand, has a more slow progressive effect. For example, after radiation therapy most men experience no significant change in the erectile function for up to a year after completion of radiation therapy. However in the ensuing 3-4 years most men will see some negative impact on their function.