Radiation therapy for prostate cancer

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 tissues. 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. Once 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 8 weeks. If cancer has spread to your bones, shorter periods of treatment may be given to specific areas to relieve pain.
• 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. As the needles are pulled out, the seeds are left in place. The surgeon uses ultrasound to locate your prostate and guide the needles. The seeds release radiation for weeks or months, after which they are no longer radioactive. The radiation in the seeds can't be aimed as accurately as external beams, but on the other hand, they are less likely to damage normal tissue. Once the seeds have lost their radioactivity, they become harmless and can stay in place indefinitely.

Sometimes treatment involves a combination of brachytherapy and low-dose external radiation. In other cases, treatment combines surgery with external radiation.

A newer form of radiation therapy, called 3D-CRT (three-dimensional conformal radiation therapy), allows doctors to use higher doses of radiation that are more accurately aimed to avoid damaging normal tissue. Use of 3D-CRT causes less serious side effects than radiation therapy. It is preferred over ordinary radiation therapy for the treatment of prostate cancer.¹

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 distant parts of your body. If it has, your doctor may offer you the option of a clinical trial for treatment.

Side effects may last only as long as the treatment, or they may continue and become chronic. Side effects include:²

• An irritated rectum and an urgent need to pass a stool. This is called proctitis.
• An inflamed bladder and urination problems. This is called cystitis.
• An inflamed intestine and diarrhea. This is called enteritis.
• Being unable to have an erection. This is called impotence.
• Being unable to control urination. This is called incontinence.
• Painful urination. This is called dysuria.
• Bleeding from the rectum or blood in the urine.

Radiation therapy is used for:

• Cancer that has not spread in generally healthy men who are younger than 70.
• Cancer that has spread to the bones, is not getting better with hormonal treatment, and is causing pain.
• Cancer that has come back in the prostate after surgery.
• Additional therapy after surgery to destroy cancer cells that may remain, especially if all the cancer cannot be removed. This is done very rarely.

For curing early stage prostate cancer, the evidence seems to show that radiation works as well as surgery.³ (No studies have directly compared radiation with surgery.)

For treating advanced prostate cancer that has grown beyond the prostate but not into lymph nodes or bones, external-beam radiation combined with hormone drugs can work better than surgery. This treatment often results in controlling cancer growth and in many years of disease-free survival.²

For stage III prostate cancer, there is evidence that combining radiation with hormone drugs improves survival rates.² One study that followed men with stage III prostate cancer for 20 years after radiation therapy showed that: ²

• 44% had no problems with prostate cancer for the rest of their lives.
• 47% eventually died of prostate cancer.

Side effects are common. Some men develop long-term problems that may have a significant impact on their quality of life. Long-term problems that can be caused by radiation treatment include:

• An irritated rectum and an urgent need to pass a stool. This is called proctitis.
• An inflamed bladder and urination problems. This is called cystitis.
• An inflamed intestine and diarrhea. This is called enteritis.
• Being unable to have an erection. This is called impotence.
• Being unable to control urination. This is called incontinence.
• Painful urination. This is called dysuria.

A newer form of brachytherapy involves placing radioactive material into the prostate and then removing the material.

This technique—also called high-dose rate, or HDR, brachytherapy—uses tiny tubes that are placed through your skin into your prostate. Radioactive material is injected into the tubes, which are left in place for 5 to 15 minutes. The tubes are removed at the end of each treatment. Generally, about 3 brief treatments are given over 1 or 2 days.

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Citations

1. National Comprehensive Cancer Network and the American Cancer Society (2004). Prostate Cancer: Treatment Guidelines for Patients, version IV, pp. 1–59. Jenkintown, PA: National Comprehensive Cancer Network.

2. National Cancer Institute (2006): Prostate Cancer (PDQ): Treatment—Health Professional Version. Available online: http://www.nci.nih.gov/cancertopics/pdq/treatment/prostate/HealthProfessional.

3. Scher HI, et al. (2005). Cancer of the prostate. In VT DeVita Jr et al., eds., Cancer: Principles and Practice of Oncology, 7th ed., pp. 1192–1259. Philadelphia: Lippincott Williams and Wilkins.