Radiation therapy uses high-energy rays to kill or shrink cancer cells, and to decrease their ability to divide. Radiation is often used to treat prostate cancer that is still confined to the prostate gland, or has spread only to nearby tissue. If the disease is advanced, radiation may be used to reduce the size of the tumor and to provide relief from symptoms.

There are generally two types of radiation therapy. However, external radiation is the usual type that is used for treatment of breast cancer. Consider the following:

• external radiation (external beam therapy) - a treatment that precisely sends high levels of radiation directly to the cancer cells. The machine is controlled by the radiation therapist. Since radiation is used to kill cancer cells and to shrink tumors, special shields may be used to protect the tissue surrounding the treatment area. Radiation treatments are painless and usually last a few minutes.
• internal radiation (brachytherapy, implant radiation) - radiation is given inside the body as close to the cancer as possible. Substances that produce radiation, called radioisotopes, may be implanted directly into the breast tumor. Internal radiation involves giving a higher dose of radiation in a shorter time span than with external radiation. Internal radiation for breast cancer is currently being studied and is considered experimental.
• radiofrequency ablation (RFA) - new technology under study uses a special probe to deliver high-energy radio waves to destroy the tumor cells.

Side effects, and the degree to which they are experienced, differ. Discuss any possible side effects of treatment with your physician prior to the procedure. Possible side effects of radiation for prostate cancer may include the following:

• diarrhea, with or without blood in the stool, and colitis

• problems associated with urination

• a degree of impotence (inability to achieve or maintain an erection), which may occur within two years of radiation therapy