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 8 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.
What To Expect After Treatment
Side effects may last only as long as the treatment, or they may continue and become chronic. Some side effects occur after treatment, such as erection problems. For some men, this problem gets gradually worse over the course of several years after treatment. The long-term effects of radiation therapy on the main body systems are not yet known. Side effects include:1
Why It Is Done
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.
- Cancer cells that may remain after surgery, especially if all the cancer cannot be removed. This is done very rarely.
How Well It Works
For early-stage prostate cancer, prostatectomy and radiation appear to work equally well. Radiation appears to work as well as prostatectomy and active surveillance for most men over 65 who have early stage prostate cancer (stages I and II, also called localized prostate cancer). For men younger than 65, treatment with surgery may help them live longer.2
For treating low-risk prostate cancer, brachytherapy alone works well.3
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.1
Radiation therapy also works well to treat pain when prostate cancer has spread to the bone.4
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.
What To Think About
The goal of radiation therapy is to deliver the highest dose possible to the prostate while protecting the rest of the nearby organs (such as the bladder and rectum) from unnecessary radiation. Newer ways of giving radiation, such as 3D-CRT, IMRT, and proton beam therapy, are more accurate. This has helped to reduce problems caused by radiation.
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National Cancer Institute (2012). Prostate Cancer Treatment (PDQ)-Health Professional Version. Available online: http://www.cancer.gov/cancertopics/pdq/treatment/prostate/HealthProfessional.
Lu-Yao GL, et al. (2010). Outcomes of localized prostate cancer following conservative management. JAMA, 302(11): 1202-1209.
Zelefsky MJ, et al. (2011). Cancer of the prostate. In VT DeVita Jr et al., eds., DeVita, Hellman and Rosenberg's Cancer: Principles and Practice of Oncology, 9th ed., pp. 1220-1271. Philadelphia: Lippincott Williams and Wilkins.
D'Amico AV, et al. (2012). Radiation therapy for prostate cancer. In AJ Wein et al., eds., Campbell-Walsh Urology, 10th ed., vol. 3, pp. 2850-2872. Philadelphia: Saunders.
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerChristopher G. Wood, MD, FACS - Urology, Oncology
Current as ofNovember 14, 2014