External beam radiation therapy treatments are normally given on a daily basis 5 days a week (Monday to Friday) for anything up to about 6 or 7 weeks and each treatment, which is painless, lasts for just a few minutes. (Such treatments are also commonly given to patients whose cancer is no longer localized to the prostate gland but has spread into the pelvis and can also be used to relieve pain and reduce tumors in cases of advanced prostate cancer.)

In cases where tumors are large it is also common to give hormone treatment alongside radiation therapy in order to block the action of the male hormones which feed the growth of prostate cancer tumors. Such hormonal treatments are often continued for many months, or even years.

External beam radiation targets not only the prostate gland but also the seminal vesicles, to which prostate cancer can readily spread. In previous forms of this treatment it was also common to irradiate the pelvic lymph nodes but today this is only done in a minority of cases where evidence suggests that this is necessary.

There are generally few immediate side-effects to external beam radiation other than fatigue and possibly diarrhea when radiation is applied to the rectum, but both of these soon pass once treatment is completed.

Longer-term affects include impotence which affects about 40% to 50% of patients. This figure is however declining with the introduction of computer technology which now allows treatment to be tailored precisely to the anatomy of the patient with far more precise targeting than has previously been possible.

Turning to internal radiation therapy, this is a procedure in which dozens of tiny seeds are implanted directly into the prostate gland to deliver a high dose of radiation directly into the affected tissue.

Ultrasound is used to guide very thin needles from the perineum into the prostate gland to deposit the tiny seeds of palladium and iodine in a pattern which has previously been mapped using a very sophisticated computer program. The procedure, which usually takes about an hour, is carried out under local anesthetic and the patient is normally allowed home the same day. One alternative approach is to use more powerful temporary seed implants which are introduced over several days and possibly to combine this with low dose external radiation therapy. This procedure does however require hospitalization.

Internal radiation therapy carries few side-effects and normally leads to impotence in less that 15% of patients under the age of 70. It is not however suitable for everybody, especially men with large tumors or those who have undergone a transurethral resection of the prostate for benign prostatic hyperplasia.