Radiation Therapy for Prostate Cancer

Treatment Overview

Radiation therapy uses high doses of radiation, such as X-rays, to destroy cancer cells. The radiation damages the genetic material of the cells so that they can't grow. Although radiation damages normal cells as well as cancer cells, the normal cells can repair themselves and function, while the cancer cells cannot.

Radiation therapy may be used alone or combined with hormonal treatment to treat prostate cancer. It is most effective in treating cancers that have not spread outside the prostate. But it also may be used if the cancer has spread to nearby tissue. Radiation is sometimes used after surgery to destroy any remaining cancer cells and to relieve pain from metastatic cancer.

Radiation is delivered in one of two ways.

• External-beam radiation therapy uses a large machine to aim a beam of radiation at your tumor. After the area of cancer is identified, an ink tattoo no bigger than a pencil tip is placed on your skin so that the radiation beam can be aimed at the same spot for each treatment. This helps focus the beam on your cancer to protect nearby healthy tissue from the radiation. External radiation treatments usually are done 5 days a week for 4 to 9 weeks. If cancer has spread to your bones, shorter periods of treatment may be given to specific areas to relieve pain.
  • Conformal radiotherapy (3D-CRT) uses a three-dimensional planning system to target a strong dose of radiation to the prostate cancer. This helps to protect healthy tissue from radiation.
  • Intensity-modulated radiation therapy (IMRT) uses a carefully adjusted amount of radiation. This protects healthy tissues more than conformal radiotherapy does.
  • Proton beam therapy uses a different type of energy (protons) rather than X-rays. This allows a higher amount of specifically-directed radiation, which protects nearby healthy tissues (especially the rectum). Sometimes proton therapy is combined with X-ray therapy. It is available only at big medical centers.
• Brachytherapy, or internal radiation therapy, uses dozens of tiny seeds that contain radioactive material. It may be used to treat early-stage prostate cancer. Needles are used to insert the seeds through your skin into your prostate. The surgeon uses ultrasound to locate your prostate and guide the needles.
  • High-dose-rate (HDR) brachytherapy uses radioactive material placed into the prostate for a very brief period of time (seconds to minutes) before being removed. The radiation is delivered this way several times.
  • Low-dose-rate (LDR) brachytherapy uses a lower dose of radioactive material that is left in place permanently.

Sometimes treatment combines brachytherapy with low-dose external radiation. In other cases, treatment combines surgery with external radiation or hormone therapy may be used along with brachytherapy.

Before radiation therapy is scheduled, your doctor probably will order a bone scan and CT scan to find out whether the cancer has spread to other parts of your body. If it has, your doctor may offer you the option of a clinical trial for treatment.