Radiation therapy for prostate cancer – Internal radiation therapy

Internal radiation therapy for prostate cancer is also called brachytherapy.  There are two main approaches that are currently being used.

The first approach involves permanent placement of about 40 to 100 “seeds” that give off low levels of radiation for up to several months.

These radioactive seeds (iodine-125 or palladium-103 are often used) are:

  • About the size of a grain of rice
  • Implanted into the prostate under anesthesia in the operating room

Small, thin needles are inserted through the skin between the scrotum and anus to place the seeds into the prostate.

Not for every man

This type of radiation therapy for prostate cancer may not be as effective in men with large prostate glands because the seeds cannot be placed everywhere they are needed.

For these men, hormone therapy may first be used to shrink the gland.

Testing first


Like external radiation, the first step involves several tests that guide the placement of the seeds, such as:

  • Transrectal ultrasound
  • CT scans
  • MRIs

Keep a distance?

Since the seeds give off low levels of radiation, the doctor may advise your loved one to keep his distance from pregnant women or small children for a period of time.

He may also be told to wear a condom during sex.

There is a rare chance that the seeds may travel in his body, but this doesn’t appear to be a serious problem.

Talk to your doctor about any concerns you have.

Temporary internal radiation therapy for prostate cancer

This type of radiation therapy is called temporary or high dose rate (HDR) brachytherapy.

  • Needles are inserted into the area between the scrotum and anus
  • Inside these needles are soft catheters that are left in place (the needles are removed)
  • The radioactive substance (either iridium-92 or cesium-137) is placed into the catheters, usually for 5 to 15 minutes
  • It’s then removed

The advantage of this approach is that most of the radiation is delivered within the prostate gland, which is designed to avoid harming:

  • Nerves
  • Urethra
  • Bladder
  • Rectum
  • Other nearby tissues

A man typically receives 3 of these treatments over several days.  The catheters are then removed.

You should know that urine may look reddish brown for several days.  A man may also have some soreness.

Both of these approaches may be combined with external beam radiation if there is a risk that the cancer has spread beyond the prostate gland.

Potential side effects

Just like external beam radiation, internal radiation therapy for prostate cancer can cause urinary problems and impotence.  Other factors include:

  • Age
  • Previous urinary or erectile problems


Bowel problems can occur, but they are usually temporary.

Frequent urination is a more common long-term side effect than severe urinary incontinence.


Return to treatments


The American Cancer Society. Prostate Cancer. http://www.cancer.org. Accessed March 17, 2015..

US TOO International, Inc. Pathways for new prostate cancer patients. http://www.ustoo.com. Accessed September 1, 2008.

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