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It’s estimated that 1 in 8 men will be diagnosed with prostate cancer in their lifetime. Prostate cancer is the second most common cause of cancer death for men in the United States only behind lung cancer.

However, the majority of prostate cancers tend to grow relatively slowly, and they have a good outlook if treated early.

Radiation therapy is one treatment your doctor may recommend for prostate cancer. It may be used either by itself or in combination with other treatment options, such as hormone therapy, active surveillance, and prostatectomy (surgery).

Keep reading as we explain how radiation therapy works for treating prostate cancer and when it’s generally used.

More than half of people undergoing cancer treatment get radiation therapy.

The treatment uses concentrated waves of intense energy to destroy cancer cells. The radiation may be in the form of X-rays, gamma rays, electron beams, or protons. These high-energy waves break down the DNA inside cancer cells and prevent them from replicating.

Radiation therapy can also damage healthy cells, but treatment seeks to minimize damage to healthy tissue. Normal cells can often recover from damage once treatment stops.

According to the American Cancer Society, radiation therapy may be used to treat prostate cancer:

  • as the first treatment for low-grade cancer contained to the prostate gland
  • as the first treatment in combination with hormone therapy for cancer that’s growing outside the prostate and into nearby tissue
  • after surgery if the surgery doesn’t completely get rid of the cancer or if the cancer grows back
  • to keep advanced cancer under control and to help prevent symptoms

Two types of radiation therapy are used to treat prostate cancer. These are external beam radiation therapy and brachytherapy.

External beam radiation therapy

During external beam radiation therapy, a machine aims beams of concentrated radiation at cancer cells in the prostate. It may be used to treat cancer in the early stages or to help relieve symptoms if cancer spreads to bone. The procedure is generally painless.

According to the American Cancer Society, people typically undergo radiation therapy 5 days per week for at least several weeks.

External beam radiation therapy can be broken into several subcategories:

  • Intensity-modulated radiation therapy. A machine connected to a computer adjusts your position as the machine delivers radiation. The intensity and angle of the beams of radiation can be adjusted.
  • Three-dimensional conformal radiation therapy. A computer maps cancer cells before radiation beams are aimed at your prostate from several directions.
  • Stereotactic body radiation therapy. Large doses of radiation are administered in a short period. Treatment is usually given over a few days.
  • Proton beam radiation therapy. Concentrated beams of protons are used to target cancer. In theory, proton beam radiation can deliver more radiation while doing less damage to healthy tissues.

Brachytherapy (internal radiation therapy)

Brachytherapy uses small radioactive pellets about the size of rice grains to kill prostate cancer cells. It’s generally only used for people with early stage prostate cancer.

Your doctor will position the pellets in your prostate with help from imaging techniques such as an ultrasound, computerized tomography (CT) scan, or magnetic resonance imaging (MRI).

Brachytherapy may be combined with external radiation if your cancer is at a high risk of growing outside your prostate.

There are two types of internal radiation therapy used to treat prostate cancer:

  • Permanent brachytherapy. Radioactive material is inserted into your skin between your scrotum and anus using a needle. The pellets give off radiation for weeks to months.
  • Temporary brachytherapy. A large dose of radioactive material is left in your prostate for about 5 to 15 minutes before being removed.

External beam radiation therapy and brachytherapy both have the potential to cause side effects. Generally, most side effects go away within 2 months of finishing treatment.

External beam therapy

Potential side effects of external beam therapy include:

Radiation proctitis

Radiation can irritate the lining of your rectum. This can lead to diarrhea, blood in your stool, or rectal leakage. In the majority of cases, these symptoms go away after treatment, but in rare cases, they may be permanent.

Radiation cystitis

Bladder irritation caused by radiation is called radiation cystitis. Symptoms can potentially include:

Symptoms generally improve shortly after treatment, although they can sometimes be permanent. Developing leaking or dribbling when urinating more commonly occurs after prostate surgery than radiation therapy.

Erection problems

After receiving radiation therapy for an extended period, you may develop erectile dysfunction. Your chance of developing erectile dysfunction increases the longer you’re on radiation.


Radiation therapy commonly causes fatigue that remains for weeks or months after treatment is finished. Most people begin to feel tired within weeks of starting radiation therapy.

Lymph node damage

Lymph nodes help circulate fluid around your body and contain immune cells. Radiation therapy can damage lymph nodes around your prostate and may lead to swelling or pain.


Internal beam therapy can cause similar symptoms as external beam radiation therapy such as radiation proctitis, trouble urinating, and erection problems.

Radioactive pellets used during brachytherapy can give off radiation for up to months. The amount of radiation is mostly contained to your prostate, but your doctor may recommend that you stay away from pregnant people or small children.

The pellets may also be picked up by detection systems at some airports, so you may want to bring a doctor’s note with you when you’re traveling.

Pellets can move, and in rare cases, they can move through your bloodstream and end up in other parts of your body such as your lungs or heart. Generally, this movement is harmless.

Your doctor can help you determine whether radiation therapy is right for you.

In addition, an oncologist — a doctor specializing in cancer treatment — can help you learn how to minimize your chance of developing side effects.

They can also refer you to local support groups where you can get in touch with other people who have undergone or are undergoing the same treatment.

Online support groups for prostate cancer

  • Us TOO. This organization has more than 200 support groups in the United States and abroad.
  • Prostate Cancer Research Institute. This website allows you to search for support groups by state.
  • Cancer Care. This site offers 15-week online support groups for people diagnosed with prostate cancer. Co-sponsored by the National Alliance of State Prostate Cancer Coalitions.
  • Male Care. This organization offers online support groups for people with prostate cancer and their partners or caregivers.
  • Imerman Angels. This support community offers one-on-one support with a mentor.
Was this helpful?

Prostate cancer is the second leading cause of cancer death in men. Radiation therapy is one potential treatment option that uses concentrated waves of energy to break down the DNA of cancer cells.

Radiation therapy can be used by itself or together with other treatments such as hormone therapy.

Your doctor can help you determine whether radiation therapy is right for you. You may find it helpful to join a support group to connect with other people who have undergone the same treatment.