Radiation oncology uses high-energy X-rays or other types of radiation to kill cancer cells. It only affects cells in the area that is being treated and is an option for men with any stage of prostate cancer.
Radiation therapy is often used as the initial treatment for low-grade cancer that has not spread outside of the prostate or that only has spread to nearby tissue. Radiation therapy also may be used after surgery to destroy any cancer cells that are still present in the area or come back (recur) after surgery. In later stages of prostate cancer, radiation treatment may be used to help relieve pain when cancer has spread to the bone.
Doctors use two types of radiation therapy to treat prostate cancer. They are external beam radiation therapy and internal radiation therapy. Some men receive both types.
External Beam Radiation
This method of delivering radiation therapy uses a machine outside the body to send radiation toward the prostate cancer. During a procedure, a patient lies on a table while a machine moves around his body and directs high-powered energy beams to the cancer cells.
This painless treatment lasts only a few minutes, and is usually given five days a week for about six to eight weeks. Before treatments start, imaging studies, such as MRIs, CT scans, or X-rays of the pelvis, are done to find the exact location of the prostate gland.
Several new techniques of external beam radiation allow doctors to give higher doses of radiation to the prostate gland while reducing the radiation exposure to nearby healthy tissues. These techniques have fewer side effects than standard external radiation therapy.
- Three-dimensional conformal radiation therapy (3D-CRT) – This procedure uses special computers to more precisely locate the prostate. A plastic mold resembling a body cast is used to keep the patient stationary to allow the radiation to be more accurate. Radiation beams are then shaped and aimed at the prostate from several directions, causing less damage to normal tissues.
- Intensity modulated radiation therapy (IMRT) - This is an advanced form of 3D therapy which uses a computer-driven machine that moves the patient as the radiation is delivered from several different angles. The intensity or strength of the radiation can be adjusted to minimize the impact to normal tissue, allowing an even higher dose to reach the cancer.
- Conformal proton beam radiation therapy - This technique uses protons (positive parts of atoms) to kill cancer cells. Protons release energy aimed at the cancer cells after traveling a certain distance. This causes less damage to the tissues they pass through before they reach the cancer cells and allows more radiation to be delivered to the prostate.
- Stereotactic radiosurgery - This method, in which an external machine delivers radiation precisely to the tumor, is most commonly used to treat cancer that has spread to the brain.
Internal Radiation Therapy or Brachytherapy
The administration of radiation from inside the body (internal radiation), is called brachytherapy. Brachytherapy is generally used only in men with early stage prostate cancer that is relatively slow growing. It also may be given with external beam radiation therapy for some patients with more advanced cancer.
Brachytherapy may not be as effective in men with large prostate glands because it may not be possible to place the seeds into all of the correct locations.
Permanent, low dose rate (LDR) brachytherapy
For this treatment, implants containing radiation called seeds are placed inside a patient’s prostate. Thin needles are first inserted through the skin in the area between the scrotum and anus (perineum) and into the prostate. The seeds are then injected through the needles to the prostate. The needles are removed, leaving the seeds in place where they administer a high quantity of low doses of radiation for several months.
The seeds are so small that the patient does not feel them. They eventually stop giving off radiation and do not need to be removed once the radiation is gone. This method allows for less damage to the healthy tissue near the prostate.
Temporary, high dose rate (HDR) brachytherapy
This is a newer technique that uses soft nylon tubes called catheters to administer the radiation. The catheters are placed inside hollow needles that have been inserted through the perineum into the prostate. The needles are then removed but the catheters stay in place. Radioactive material is placed in the catheters and administers treatment for approximately 5 to 15 minutes. Usually three brief treatments are given, and the radioactive substance is removed each time. The catheters are removed when the treatment is completed.
HDR is often combined with external beam radiation. When combined, it is given at a lower dose than if used by itself. The advantage of this approach is that most of the radiation is concentrated in the prostate gland itself, sparing the urethra and the tissues around the prostate such as the nerves, bladder and rectum.