External beam radiation therapy

Radiation therapy is sometimes used when prostate cancer has not spread beyond the prostate gland or has spread only to nearby tissues. If prostate cancer has spread, radiation therapy may be used to help shrink the tumor or to reduce symptoms when cure is not possible.

For radiation therapy, high-powered X-rays are precisely focused through the body to the prostate gland to kill cancer cells and interfere with cancer cells' ability to reproduce. This method has been used to treat prostate cancer for decades. When radiation is directed from outside the body through the body to the cancer, it's called external beam radiation, or EBR.

Five to eight years after treatment, results of external beam radiation are equal to those of surgery when treatment is for cancer that has not spread beyond the prostate.

External beam radiation effectively destroys cancerous cells in the treated area, but it can also damage healthy tissue next to the prostate. To limit damage to surrounding tissue, a radiology specialist maps out the precise area of your body that needs to receive radiation. To do this, a body supporter holds you in the same position for each treatment. You're asked to arrive with a full bladder for therapy. This pushes most of your bladder out of the path of the radiation beam. Ink marks on your skin help the radiation therapist hit the same targets each time. Custom-designed shields help protect nearby normal tissue — such as the intestines, anus and rectal wall — from the radiation.

Radiation treatments are generally given five days a week for about six to eight weeks on an outpatient basis. Each treatment appointment takes about 15 minutes. However, much of this is preparation time — radiation is received for only several minutes. Anesthesia is not needed with external beam radiation because there's no sensation of pain during treatment.

The various forms of external radiation include intensity-modulated radiation therapy (IMRT), proton beam and three-dimensional conformal radiation therapy (3D-CRT).

• IMRT. This method of external radiation uses computerized tomography (CT) scanning to get detailed pictures of the tumor shape to help plan precise radiation doses. This technique helps protect surrounding tissues, enabling the therapist to use a higher dose. Long-term outcomes show that about nine out of 10 men receiving IMRT are disease-free after eight years.
• Proton beam. This method uses protons instead of radiation to kill the cancer. Protons are parts of atoms that cause little damage to surrounding tissue but effectively destroy cells at the end of the beam. The protons travel through noncancerous tissue and come to rest in the targeted area, where they deposit their radiation dose. This allows your therapist to deliver stronger doses of beam radiation.
• 3D-CRT. Three-dimensional scans are often used to determine the exact location of your prostate and surrounding structures. Computer-imaging software gives radiation therapists the ability to find the best angles to fire the beams of radiation. By using new techniques — which allow for more precise focusing of the radiation beams — greater doses of radiation can be administered to your prostate without harming surrounding tissue, which improves the chances of curing the prostate cancer. This technique preceded IMRT and has been replaced by IMRT in most modern radiotherapy practices.

Side effects of external beam radiation therapy
Side effects of radiation therapy include sexual, urinary and rectal problems, appetite loss, and fatigue. Some side effects are long term, and others, such as fatigue and appetite loss, usually go away a couple of months after treatment.

In the last 10 years, radiotherapy complications from external beam radiation have been steadily declining due to better selection of men who would likely benefit from the treatment and due to improved radiation treatment techniques.

• Sexual function. Radiation therapy can affect your sexual function. Most men don't have problems with erections or intercourse immediately after radiation therapy. However, long-term effects can damage nerves that control erections and arteries that carry blood to the penis. One-third to one-half of men who undergo radiation therapy for early-stage prostate cancer may develop erectile dysfunction or impotence as a complication of treatment. The younger you are at the time of treatment, the better your chance of retaining normal sexual function. Oral medications, penile injections or insertion of medications into the urethra, and vacuum pumps can, in most cases, help maintain an active sex life after treatment.
• Urinary problems. The most common urinary problems are constantly feeling as if you have to urinate, burning or pain while urinating, frequent urination, blood in the urine and urine leakage. Most of these problems are temporary and gradually get better in a few months after completing treatment. You may need medication to treat these symptoms, and some men need to use self-catheterization to help them urinate. A few men have severe and sometimes permanent symptoms. Urinary symptoms tend to be worse and last longer with radioactive seed implants than with external beam radiation.
• Rectal problems. Rectal problems — including diarrhea, rectal bleeding, rectal urgency (a sense that you have to have a bowel movement) and discomfort during bowel movements — develop in fewer than one in 10 men undergoing radiation treatment. Men have fewer rectal complications with radioactive seed implants than they do with external radiation. Medications can help control these symptoms. Men treated with external beam radiation may have an increased risk of rectal cancer; however, the studies on this relationship are conflicting.
• Other side effects. Radiation therapy can also cause fatigue, hair loss and loss of appetite. Energy levels and appetite usually return within a couple of months after treatment.
• Late effects. Some men develop new side effects several years after finishing radiation therapy. Side effects such as urinary incontinence and sexual dysfunction can occur with either external beam radiation or radioactive seed implants, although those treated with radioactive seed implants have more severe symptoms.