Radiation Side Effects Overview

High doses of radiation are used to target and destroy cancer cells. To help ensure that all the cancer is destroyed, doctors deliver radiation with a margin (an area of healthy cells), surrounding the cancer area. This is to ensure that no abnormal cells are missed.


During and after treatment, the radiation damages both cancerous and healthy cells. The cancerous cells are not able to repair themselves and heal, while the healthy cells can typically heal. This is the reason for treating in several fractions (small doses over several days), which gives healthy cells a chance to recover. The cells recovering is what often causes fatigue — the most common side effect of radiation therapy.

Each organ in the body or type of tissue can withstand certain amounts of doses of radiation. When radiation is delivered to different areas of the body, different side effects will occur. Some side effects are short-term, while others are longer-term. Some side effects are enhanced or made worse by concurrent chemotherapy treatments.

The type and severity of side effects you have with external beam radiation for prostate cancer vary from person to person.   Most side effects are temporary, can be controlled and generally improve over time once treatment has ended.

Potential side effects of external beam radiation therapy for prostate cancer may include:

  • Frequent urination
  • Difficult or painful urination
  • Blood in the urine
  • Urinary leakage
  • Abdominal cramping
  • Diarrhea
  • Painful bowel movements
  • Rectal bleeding
  • Rectal leaking
  • Fatigue
  • Sexual dysfunction, including diminished erectile function or decrease in the volume of semen
  • Skin reactions (similar to a sunburn)
  • Secondary cancers in the region of the radiation

Most of the side effects are mild and tolerable. Some side effects may develop months to years later. Serious late side effects aren’t common. Ask your doctor about potential side effects, both short- and long-term, that may occur during and after your treatment.

You and Your Cancer Team

Your cancer care team can tell you about your treatment, likely side effects, and things you need to do to take care of yourself. They can also talk to you about any other medical concerns you have. Tell them about any changes you feel and any side effects you have. Be sure that you understand any home care instructions and know who to call if you have more questions. Also be sure you know what to do if you need help after office hours, in case you have problems at night or on the weekend.

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