The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on October 27, 2021.

Radiation therapy for prostate cancer

Radiation therapy uses invisible, high-energy radiation to destroy cancer cells. The two main types of radiation therapy used in prostate cancer treatment are: external beam radiation and internal radiation therapy (often called brachytherapy). They differ in the way the radiation is delivered to a tumor. Whether a prostate cancer patient receives external or internal radiation therapy generally depends on several factors, including the type, size, stage and location of the tumor.

This guide covers the most common radiation treatments for prostate cancer to help patients understand what to expect.

What is a radiation oncologist?

If a patient is undergoing radiation, the cancer treatment plan may be managed by a radiation oncologist who carefully monitors the person’s overall health and well-being through the process.

With advanced cancer, a patient may also be referred to a medical oncologist. This specialized doctor uses medicines such as chemotherapy and hormone therapy to treat cancers. It’s common for several medical specialists to work together on a treatment plan—they’re known as a cancer care team.

External beam radiation therapy (EBRT)

External beam radiation therapy (EBRT) uses high-energy rays (X-rays) to kill cancer cells. A machine delivers radiation beams to the precise area where the tumor is located. Because the prostate may move during radiation treatment, as a result of breathing and normal movement in the intestines, healthy tissue near the prostate may be affected.

The procedure lasts only minutes, but it may take some time to position the patient correctly and get everything ready. There’s typically no pain or discomfort during the procedure. In most cases, EBRT may be administered in several sessions throughout the course of a few weeks.

Below are EBRT techniques commonly used in the treatment of prostate cancer.

Three-dimensional conformal radiation therapy (3D-CRT)

This image-guided radiation therapy uses computers to create a 3D map of the prostate. This allows for more precise radiation, with beams targeting cancer cells and avoiding damage to healthy cells.

Intensity-modulated radiation therapy (IMRT)

This is a highly advanced form of 3D-CRT that uses technology to control the radiation machine. It allows for higher doses of radiation, and the precision may reduce the risk of side effects. It’s also the most common type of EBRT cancer radiation therapy. IMRT may be a treatment option for patients with prostate cancer that has not spread. The therapy may also be an option for patients with recurrent prostate cancer who have received radiation therapy for their cancer in the past.

Stereotactic body radiation therapy (SBRT)

This type of radiation therapy may be a treatment option for patients with early-stage prostate cancer. It delivers high doses of highly focused radiation beams to the prostate. Typically, SBRT is delivered to a patient over the course of five days.

Proton beam therapy

This procedure uses high proton beams instead of X-rays to deliver radiation. Proton beams may do less damage to cells as they pass through, sparing healthy tissues. However, the effects of radiation therapy using proton beams are still being studied, so this therapy isn’t widely available.

Side effects of EBRT for prostate cancer

Many of the possible side effects of radiation therapy for prostate cancer involve the bladder and bowel—the prostate is very close to both. Although the goal is to target only the prostate with radiation, sometimes small amounts may cause problems to nearby areas of the body.

Some of the potential side effects from EBRT include:

  • Bowel problems, including diarrhea, leakage or rectal bleeding
  • Urinary symptoms, such as a need to urinate more frequently, incontinence or a burning sensation during urination
  • Fatigue
  • Erectile problems or sexual function changes
  • Lymphedema (swelling and discomfort caused by damage to the lymph nodes during radiation)

Internal radiation therapy (brachytherapy)

Unlike EBRT, which is an external treatment, brachytherapy is a type of internal radiation therapy. It may be used to treat small or slow-growing cancers, with a low PSA score and a low risk of cancer spread.

With brachytherapy, small seeds of radioactive material, sometimes called radiation seeds, are placed in the body, releasing radiation that works to destroy cancer cells over time. Brachytherapy may be administered in high or low doses.

The two main types of internal radiation therapy treatments differ in the rate at which radiation is delivered. These two types are:

Low dose rate (LDR) brachytherapy implants 

The most common form of brachytherapy for prostate cancer, LDR involves surgically placing small radioactive pellets, about the size of a grain of rice, within the prostate. Once put in place, they remain there for life, but the radiation weakens over weeks or months, until it almost completely goes away.

High dose rate (HDR) brachytherapy

With HDR brachytherapy, a higher radiation dose is given for a shorter period of time. The exact treatment plan varies based on the cancer characteristics, but patients often have the radiation source put into place through a catheter for five to 15 minutes a few times over two days.

Side effects of brachytherapy for prostate cancer

Brachytherapy may irritate the rectum, causing a condition called radiation proctitis. This usually causes short-term issues such as burning, rectal pain and diarrhea. Urinary incontinence, usually caused by irritation of the urethra, is also generally short term. Some patients may experience erectile dysfunction after brachytherapy.

Discomfort and temporary tenderness may occur when the catheter for HDR brachytherapy is first removed.

SpaceOAR System

The SpaceOAR® System may also be incorporated during radiation therapy for prostate cancer to reduce the radiation dose to the rectum. SpaceOAR is a temporary, injectable gel that creates about a half-inch (or 1.3 cm) of space between the prostate and the rectum. The gel stays in the body for about three months, and then is naturally absorbed and eliminated from the body in the urine. By separating the prostate from the rectum and reducing radiation exposure, the gel is designed to reduce, or possibly eliminate, damage to the rectum and associated side effects.

Radiation therapy for advanced prostate cancer

When prostate cancer spreads, it tends to travel first to the bones. This may be diagnosed using imaging tests such as computed tomography (CT) scans. Cancer in the bones may cause pain and discomfort, so radiation is one tool that doctors may recommend to help manage the disease. Other commonly used treatments for advanced prostate cancer include chemotherapy, hormone therapy or immunotherapy.

External radiation therapy may be used to help reduce bone pain by targeting specific tumors, especially on the spine.

Some patients with advanced cancer may qualify to be part of a clinical trial involving radiation. In clinical trials, researchers study the effect of new treatments to see whether these are as safe and comprehensive as current treatments, or better.