External beam radiation therapy uses high-energy x-rays beamed from a machine called a linear accelerator to kill cancer cells.
Intensity modulated radiation therapy (IMRT) is a type of external beam cancer treatment that conforms the radiation beam to the size, shape and location of a tumor. With conventional external beam radiation, directing the beam at the cancerous tissue without damaging surrounding healthy tissue is difficult.
With IMRT technology, sophisticated algorithms are used to determine the optimal dose of radiation for each area of the prostate. Then the radiation is delivered according to the treatment plan by a computer-controlled collimator mounted on the end of a linear accelerator. As the collimator rotates around the patient, its shutter leaves shift to form specific patterns that regulate the amount of radiation administered to the healthy tissue while delivering intense radiation to the cancerous tumor.
This type of therapy generally involves treatments five days a week for eight or nine weeks. In many cases, if the tumor is large, hormone therapy may be started at the time of radiation therapy and continued for several years.
External beam radiation therapy is commonly used to treat men whose cancers have spread too widely in the pelvis to be removed surgically, but have no evidence of spreading to the lymph nodes.
Brachytherapy kills cancer cells through the use of high-energy x-rays that are delivered to the prostate from dozens of tiny radioactive seeds implanted directly into the prostate gland. This approach, known as interstitial implantation or internal radiation therapy, has the advantage of delivering a high dose of radiation to tissues in the immediate area, while minimizing damage to healthy tissues such as the rectum and bladder. When the cancer is localized, brachytherapy serves as an alternative to surgery.
As practiced today, internal radiation therapy relies on ultrasound or CT to guide the placement of thin-walled needles through the skin of the perineum. Seeds made of radioactive palladium or iodine are delivered through the needles into the prostate, according to a customized pattern—using sophisticated computer programs—to conform to the shape and size of each man's prostate.
The procedure is done under general anesthesia and typically lasts 1 to 2 hours after which the patient goes home. Hormone suppression therapy is sometimes used for a few months before the radioactive seeds are implanted to shrink the prostate.