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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. Radiation damages normal cells as well as cancer cells. But 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 works best to treat cancers that haven't 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 therapy to treat prostate cancer can be done in two ways. When it's given from a machine outside the body, it's called external beam radiation, or EBRT. When radiation is placed inside the body, it's called internal radiation, or brachytherapy.

Sometimes treatment combines brachytherapy with low-dose external radiation. In other cases, treatment that 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 if 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.

Radiation treatments to the prostate can injure the rectum, which is behind the prostate. Your doctor may suggest using a hydrogel spacer. It's a water-based gel. Before you have radiation treatments, the gel is injected into the space between the prostate and rectum. The gel quickly becomes solid, and it stays solid for about 3 months. After that, it dissolves. The spacer shields the rectum from much of the radiation aimed at the prostate.

Types of radiation

Radiation therapy to treat prostate cancer can be done in two ways:

External beam radiation therapy.
This uses a large machine to aim a beam of radiation at your tumour. A tiny ink tattoo may be placed on your skin so that the radiation beam can be aimed at the same spot for each treatment. This helps protect nearby healthy tissue from the radiation.
Internal radiation therapy (brachytherapy).
This is done with tiny seeds that contain radioactive material. The doctor uses needles to insert the seeds into your prostate. They're placed through the skin between your anus and scrotum (perineum). The doctor uses ultrasound to locate your prostate and guide the needles.

Sometimes prostate cancer is treated with both external and internal radiation therapy.

What To Expect

The side effects of radiation therapy for prostate cancer may include:

  • Feeling very tired (fatigue).
  • Loss of appetite.
  • Skin changes, if you have external radiation. The skin in the treated area may look and feel sunburned.
  • Urinary problems. These may include pain when you urinate, urinating often, a strong urge to urinate, or passing blood in your urine.
  • Bowel problems. These may include pain in your rectum, diarrhea, blood in your stool, and leaking stool.
  • Erection problems. It may be difficult to get or keep an erection. These problems may slowly get worse over the course of several years.

Some side effects start during treatment and go away when it's finished. Others start later and may become long-term problems. Your medical team can tell you what to expect from the type of radiation therapy you have. And they may have ideas that will help you manage the side effects.

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 hormone 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.

How Well It Works

For men with localized prostate cancer, radiation works about as well as surgery to treat the cancer. With either treatment, the chance of the cancer spreading is low. One study looked at men who had localized prostate cancer and found that the risk of dying was very low (about one out of 100 men). The study found that the risk of dying was about the same, no matter which treatment the men chose.footnote 1

For men with advanced prostate cancer that has grown beyond the prostate but not into lymph nodes or bones, external-beam radiation combined with hormone therapy can work better than surgery. This treatment will often control cancer growth and give men many disease-free years.footnote 2

Radiation therapy also works well to treat pain when prostate cancer has spread to the bone.footnote 3


Radiation treatment for prostate cancer may increase your risk of having another cancer later in life. These may include bladder or rectal cancer.

For men with higher-risk prostate cancer, radiation treatment may be given along with hormone therapy. Hormone therapy has side effects, such as the loss of bone density and muscle mass. It can also increase the risk for bone fractures, diabetes, and heart disease.



  1. Hamdy FC, et al. (2016). 10-year outcomes after monitoring, surgery, or radiotherapy for localized prostate cancer. New England Journal of Medicine, 375(15): 1415–1424. DOI: 10.1056/NEJMoa1606220. Accessed November 3, 2016.
  2. National Cancer Institute (2012). Prostate Cancer Treatment (PDQ)—Health Professional Version. Available online:
  3. 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.


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