Prostate cancer occurs when some cells in the prostate gland grow abnormally. Cancer is a rapid growth of these abnormal cells that may invade and destroy nearby tissues and organs or spread to other parts of the body. Prostate cancer is most commonly found in the posterior or back portion of the prostate gland which is closest to the rectum, but may also arise in other locations or sites in the prostate gland. If prostate cancer can be detected early while it is confined to the prostate gland, proper treatment may result in a complete cure. Early stage prostate cancers can be treated with brachytherapy alone. More advanced prostate cancers may require a type of external beam radiation called IMRT. IMRT stands for intensity modulated radiation therapy, and is used to deliver a very precise field so that adjacent structures are not radiated along with the prostate tissue.