Radiation Therapy

Prostate Cancer Radiation Therapy

Radiation therapy uses high-energy X-ray or particle beams to kill cancer cells or keep them from growing. Typically it is a local treatment, affecting only the area of the body being treated.

Radiation therapy is one of the most common treatments for cancer and is an option for men with various stages of prostate cancer. If you have early-stage, localized prostate cancer, your doctor will probably give you a choice of treating your disease with either radiation or surgery (radical prostatectomy) since cure rates are about the same for both of these treatments and at this point no studies have definitively established that one treatment is better than the other. Radiation also may be used after surgery if your cancer returns or in combination with other therapies if you have advanced prostate cancer. In the latter case, radiation may be used to provide pain relief at sites where the cancer has spread, such as the bone.

Radiation therapy is provided at several Seattle Cancer Care Alliance (SCCA) locations. Two main types are used for prostate cancer: internal radiation therapy and external-beam radiation therapy. Some men with prostate cancer may have both types.

Internal Radiation Therapy

For prostate cancer, internal radiation therapy typically means brachytherapy. In addition, an injectable radiation therapy was approved in 2013 to treat advanced prostate cancer.


In brachytherapy, radioactive seeds are surgically implanted in the prostate to kill the cancer. The procedure takes about one-and-a-half hours. You may receive a general or a spinal anesthetic beforehand. The seeds are left in place and deliver low doses of radiation for weeks or months. The radiation typically travels only a short distance, which limits exposure to healthy tissues.

Brachytherapy is generally used in men with early-stage prostate cancer that is relatively slow growing. It may not be appropriate for more advanced prostate cancer and may also be limited by other technical factors. For example, it may not be suitable in men with large prostate glands, which makes correct placement of the seeds more complicated.

Radium 223 Dichloride (Xofigo)

In May 2013, radium 223 dichloride was approved to treat advanced prostate cancer that has become resistant to testosterone-lowering treatments and has spread to the bones. This form of radiation therapy is administered by intravenous (IV) injection every four weeks for six cycles.

External-Beam Radiation Therapy

External-beam radiation therapy aims radiation beams from outside your body at your cancer. This treatment can be used to cure localized prostate cancers or help relieve symptoms of cancer that has spread. It is typically given five days a week for seven to nine weeks, using a machine that looks like an X-ray machine. Getting in place for the treatment typically takes longer than the treatment itself, which lasts only a few minutes. The procedure is not painful.

Depending on your exact needs, your radiation oncologist will likely recommend one of three forms of external-beam radiation therapy: proton therapy, intensity modulated radiation therapy (IMRT), or volumetric modulated arc therapy (VMAT).

Normal daily variation in your internal anatomy and the position of your prostate, bladder, and rectum presents challenges to delivering external radiation to your cancer while minimizing effects on your healthy surrounding tissue. Before you begin treatment, imaging tests are done to find the exact location of your prostate. Marks made on your skin and body molds may be used to focus the radiation beams accurately during each treatment session.

GPS for the Body

SCCA incorporates the latest technology to provide the most precise treatment possible. Our radiation oncologists were instrumental in developing the Calypso System, also known as GPS for the Body. We use this system to detect even the slightest tumor movement during radiation treatments so your tumor gets the right amount of radiation and other nearby organs don’t receive radiation that is not meant for them.

The position of the target tissue is tracked using radiofrequency waves from miniature Beacon electromagnetic transponders implanted in your prostate in an outpatient procedure much like a biopsy. Your radiation oncologist uses signals from the transponders to accurately align your prostate before each session and to monitor the position of your prostate at all times during the session. If your prostate moves outside of the thresholds set for your treatment, this is adjusted for in real time to make sure you get the most precise treatment possible.

Proton Therapy

Proton therapy is an advanced form of radiation treatment. Because doctors can focus proton beams so precisely on tumors, limiting radiation to surrounding healthy tissues, proton therapy is recommended most often for anatomically complex tumors, where it’s imperative to avoid damaging nearby organs and other structures. This makes it a good option for prostate cancer. Learn more about proton therapy for prostate cancer.


IMRT uses a computer-controlled linear accelerator to move around the patient to deliver radiation. In addition to shaping the beams and aiming them at the tumor from several angles, the intensity of the beams can be adjusted to lessen the dose that reaches sensitive normal tissue. This technique may be used if tumors are near important structures.


Similar to IMRT, VMAT typically takes even less time, as the linear accelerator rotates around the patient in a continuous arc. This may permit even more precisely tailored radiation plans and benefit patients who find it difficult to be still for the usual treatment duration. Monitoring tools and 3D volumetric imaging allows doctors to accurately locate the tumor and precisely deliver the dose.

Side Effects of Radiation Therapy

Normal cells that are near your cancer may be affected by radiation, which can lead to side effects. The side effects and the time it takes to get over them vary greatly from person to person and depend on the type and dose of radiation and your overall health.

The most common short-term side effects of radiation therapy for prostate cancer include fatigue, slight reddening of the skin in the treatment area, temporary lowering of blood counts, and urinary and bowel side effects. Brachytherapy and radium 223 dichloride may have some additional or different side effects.

Talk with your treatment team about the side effects that are most common with your treatment and about the possible long-term effects. Your doctor may give you medicines to prevent or relieve side effects. For general advice, see the symptom management section. Read more about potential urinary and sexual side effects of prostate cancer treatment.