External Beam Therapy

External beam radiation therapy (also called radiotherapy) involves a series of daily treatments to accurately deliver radiation to the prostate. Radiation therapy can be as effective, and sometimes better than surgery to treat prostate cancer.

Before treatment begins your radiation oncologist will develop a treatment plan using information from your biopsy, imaging and physical exam. A CT scan is done in the position you will be treated, often with a supportive device to keep you comfortably in the same position for treatment. This is often called pre-treatment mapping (scan). Sometimes you will be asked to have a full bladder and/or a gel may be placed between your prostate and rectum to minimize side effects. Radiation oncologists may also place marker seeds (not radioactive) in your prostate to help target the prostate better. Your treatment plan will include not only the prostate, but can sometimes include the seminal vesicles (glands on the back of the prostate) and lymph nodes. Ask your doctor to explain what treatment area is appropriate for you.

With CT scans, 3-D targets of the prostate and normal tissues are created. These treatment plans focus radiation beams on the prostate while limiting radiation to healthy tissues around it such as the bladder and rectum. Intensity modulated radiation therapy (IMRT) and imaging guided radiation therapy (IGRT) are treatment approaches that allow the radiation beams to treat the cancer and lessen the risks of side effects.

External beam radiation therapy can be delivered using a variety of techniques. With all external beam therapy, treatment is delivered in a series of daily sessions, Monday through Friday, for several weeks. Each treatment is non-invasive, painless and similar to a long X-ray; you hear noise but will feel nothing at the time of treatment.

Hypofractionated radiation is a form of external beam treatment giving slightly higher doses over four to six weeks compared to a more standard treatment time of seven to nine weeks. Studies have shown similar results compared to standard treatment times. Stereotactic body radiation therapy (SBRT) is a technique for treating cancers in five or fewer treatments at substantially higher doses over one to three weeks.

SBRT is currently being evaluated for long-term side effects and may be considered for certain patients.

In most cases, external radiation is in the form of high-energy photons, or X-rays. In a few clinics around the country, proton beam therapy is used to treat prostate cancer. Proton therapy is a form of external beam radiation therapy that uses protons rather than photons to treat cancer cells. Protons may be considered for certain patients. Protons compared to photons in treating prostate cancer patients continues to be studied.

The length of your treatment will depend on your health and the type of radiation used.