Radiation therapy for prostate cancer

This page was reviewed under our medical and editorial policy by

Kevin King, MD, Radiation Oncologist, City of Hope | Downtown Chicago

This page was updated on December 22, 2023.

Radiation therapy uses invisible, high-energy radiation to destroy cancer cells. When treating prostate cancer, radiation therapy may be used:

  • As a stand-alone treatment
  • In combination with other treatments, such as hormone therapy
  • If the cancer recurs after surgery
  • As a palliative treatment for advanced cancer to help shrink tumors that may be causing pain by pressing against bone or organs

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.

Types of radiation therapy for prostate cancer

The two main types of radiation therapy used in prostate cancer treatment are:

These 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, and location of the tumor.

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

EBRT for prostate cancer

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)

IMRT is a highly advanced form of 3D-CRT that uses technology to control the radiation machine. IMRT is the most common type of EBRT cancer radiation therapy. It may be a treatment option for patients with prostate cancer that hasn't 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.

IMRT side effects

IMRT allows for higher doses of radiation, and the precision may reduce the risk of side effects. However, some prostate cancer patients who receive IMRT may experience side effects, including:

  • Changes in urination, such as increased frequency or urgency
  • A change in bowel movements, including rectal bleeding or diarrhea
  • Soreness around the rectum
  • Skin issues, such as redness or rashes
  • Hemorrhoids
  • Erectile dysfunction 

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.

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 for early-stage prostate cancer, sometimes small amounts may cause problems to nearby areas of the body.

The potential side effects from EBRT are typically the same as those for IMRT. 

Brachytherapy for prostate cancer

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. In some cases, it may be used as a boost after EBRT is given.

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 at a slow rate of delivery or at a faster delivery rate.

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

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. If you undergo LDR therapy, the care team may advise you to take certain precautions to avoid exposing others to radiation until it leaves your system.

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 a few 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. Other potential side effects of brachytherapy include:

  • Short-term urinary incontinence
  • Erectile dysfunction
  • Discomfort and temporary tenderness when the catheter is removed

SpaceOAR and Barrigel

SpaceOAR® or Barrigel® may also be incorporated during radiation therapy for prostate cancer to reduce the radiation dose to the rectum. These are temporary, injectable gels that create 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.

Potential complications associated with injection of the gel include:

  • Pain, inflammation or discomfort at the injection site
  • Infection
  • Bleeding
  • Constipation
  • Urinary retention

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 treat or 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.

The care team may recommend a systemic radiation therapy for some patients with metastatic prostate cancer. These therapies are injected or infused directly into the patient to target the disease, and include Pluvicto® and Xofigo®.

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.

Managing radiation therapy side effects

Patients who receive radiation therapy for prostate cancer may experience a wide range of short-term and long-term side effects. And side effects may vary widely from patient to patient depending on a variety of factors, including the extent of the disease and the patient’s overall health. For instance, some patients may need a urinary catheter to help empty the bladder. Other patients may experience sexual side effects.

The patient's care team will work closely with him or her to determine how best to address radiation therapy side effects. Services may include:

  • Pelvic floor therapy
  • Oncology rehabilitation
  • Behavioral health and sexual wellness counseling
  • Pain management

Learn how to decide between radiation therapy or surgery for prostate cancer

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