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Radiation Therapy Side Effects
Last Reviewed: August 26, 2021

Because the prostate is close to several vital structures, radiation therapy can disrupt normal urinary, bowel, and sexual functioning.

Short-term Complications

You may experience some temporary urinary symptoms, such as waking up in the night and needing to urinate, needing to urinate more often during the day, or urgency – needing to urinate right now, and not being able to hold it in for a long time.  Tell your doctor; there are medications that can help reduce acute symptoms.  You may also experience some rectal problems, including the need to have a bowel movement more often than usual, or loose stools.  Diarrhea is rare, but if needed, there are medications that can help. Your doctor may also suggest that you try a low-fiber diet for a while.  A device called a rectal gel or spacer (SpaceOAR) further reduces rectal side effects of radiation therapy. Ask your physician if they offer SpaceOAR at their practice and if your insurance covers it.

Long-term Complications

The risk of long-term problems after radiation therapy is very low, less than 5 percent.  These may include proctitis (rectal inflammation), cystitis (bladder inflammation), urinary or rectal bleeding, narrowing of the rectum or urethra, chronic diarrhea or urinary frequency or urgency, or development of an ulcer in the rectum.  All of these can be managed.

Erectile Dysfunction

Similar to surgery, damage to blood vessels and nerves after radiation therapy can result in decreased erectile function over time. In general, radiation therapy has less of an impact on erectile function in the first 5 to 10 years after treatment compared with surgery, and approximately 60-85% of men who have baseline erectile function before treatment will keep erectile function after treatment. Radiation therapy has delayed effects on erectile function vs. surgery; within 15 years after treatment, the rates are similar to those who underwent surgery.

These rates do not appear to be affected in the long-term by the use of short-term (4 to 6 months) hormone therapy, but are more likely to be affected by the use of long-term (18 to 36 months) hormone therapy.

Newer techniques in radiation therapy, termed “vessel-sparing” radiation therapy, have shown promising results for improving the preservation of erectile function, with close to 90% of men maintaining baseline function. Ask your radiation oncologist about vessel-sparing radiation therapy.

Other Complications

There are also fertility impacts from radiation therapy.

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