Side Effects of Radiation Therapy

Although patients do not feel anything during a radiation treatment, the effects of radiation gradually build up over time. Most patients have very few initial side effects; however, many patients experience fatigue as treatment continues.

The vast majority of patients are able to complete radiation therapy without significant difficulty. The chance of experiencing side effects, however, is highly variable. A dose that causes some discomfort in one patient may cause no side effects in other patients. If side effects occur, you should inform the technologists and radiation oncologist, because treatment is almost always available and effective.

Side effects increase with patient age and decrease as a result of more targeted radiation to the prostate. Its best to discuss the risk of various side effects with your treating physician as they can vary between treatment facilities and the various methods of radiation delivery utilized.  Radiation therapy for prostate cancer mainly causes bowel and bladder dysfunction and impotence.

Bowel Dysfunction:

Diarrhea or frequent stools, an inability to control bowel movements, and rectal bleeding are more common following EBRT than any other primary therapy and are referred to as radiation proctitis. With EBRT about 10%-20% of men experience these side effects 2 years from treatment and this has decreased to ~5% with use of IMRT which is similar to that occurring with brachytherapy. Side effects to the bowel following surgery are uncommon.

Urinary Dysfunction:

The leaking of urine or urinary incontinence, and irritative symptoms that occur with urination such as urgency, pain, and more frequent urination occur following radiation.  Incontinence can be quite severe ranging from minor leakage to complete loss of bladder control. These side effects are typically caused by damage to the nerves and muscles that control urinary function.  Over 70% of men have leakage or incontinence within six months after seed implantation, but the rate drops to 25% or less after two years and to under 10% by three years. External beam radiotherapy can irritate both the bladder and the urethra, causing inflammation or swelling of the prostate. Most of the symptoms lessen over time with little or no intervention: approximately 40% of men report irritative voiding symptoms after six months, and the majority resolve by one year, with less than 10% of men still having significant problems after three years.


Regardless of whether the nerves were spared during surgery or whether the most precise dose planning was used during radiation therapy, nearly all men will experience some erectile dysfunction (ED) for the first few months after local treatment of prostate cancer. This is because the nerves and blood vessels that control the physical aspect of an erection are incredibly delicate, and impacted by surgery or radiation. Overall 35%-60% of men will experience some erectile dysfunction. About 25-50% of men who undergo brachytherapy will experience ED vs nearly 50% men who have standard EBRT and this does not tend to improve over time.  Memorial Sloan Kettering Cancer Center reported that 43% of men treated with 3D CRT experienced ED compared to 53% for those treated with brachytherapy suggesting more precise delivery of radiation may reduce the occurrence of ED.  Men with other diseases or disorders that impair their ability to maintain an erection, such as diabetes or vascular problems, will have a more difficult time returning to pre-treatment function.

Urethral stricture:

The tube that carries urine from the bladder out of the body may, rarely, be scarred and narrowed by radiation. This can cause problems with urination, and may require further treatment to open it up again.


Fluid buildup in the legs or genitals is possible if the lymph nodes receive radiation.

Other Common Side Effects of Radiation Therapy

Skin reaction:

A common side effect of radiation therapy is skin irritation in the area of the body that is being treated. The skin reaction can range from mild redness and dryness (similar to a sunburn) to severe peeling (desquamation) of the skin in some patients. The majority of skin reactions to radiation therapy go away a few weeks after treatment is completed. In some cases, the treated skin will remain slightly darker than it was before and it may continue to be more sensitive to sun exposure.

It is important to notify your nurse or physician when your skin becomes irritated because redness and dryness can eventually progress to peeling with oozing of fluid in the area. They can suggest measures to relieve your discomfort and possibly minimize further irritation. There are effective topical medications for treatment of radiation induced skin irritation, as well as a number of precautions that may minimize skin irritation during radiation therapy, such as:

  • Keep the treated area dry and free from irritation. Cornstarch, gently patted on with a powder puff, will keep the skin dry.
  • Wash the skin in the treatment area only with mild soaps.
  • Use a mild shampoo, such as baby shampoo, if the head is being treated.
  • When using a towel, pat the area dry instead of rubbing.
  • If you must shave in the treated area, use an electric razor to prevent cuts.
  • Avoid using shaving lotions or scented creams.
  • Do not use perfumes, deodorants, or makeup in the treated area.
  • Avoid using heating pads or ice packs on the skin in the treated area.
  • Wear loose-fitting clothing that does not rub on the skin in the treated area.
  • Avoid harsh fabrics over the treatment area, such as wool, corduroy, or starched cloth. Lightweight cotton is recommended.
  • Avoid sun exposure in the treated area. If you expect to be in the sun for more than a few minutes, wear protective clothing (such as a hat with a broad brim and shirt with long sleeves) and use a sunscreen. Ask your doctor or nurse about using sunscreen lotions of SPF 15 or higher.
  • Check with your nurse or physician regarding the use of creams or lotions. Usually, samples of safe topical medications are available in the radiation clinic.
  • Unless necessary, do not use adhesive tape, including band aids and paper tape on the treated area.
  • Do not swim in salt water, lakes, pools, or ponds.
  • Always report any discomforts or concerns to your nurse or doctor.


Fatigue is a feeling of tiredness, weariness, weakness, exhaustion, or a profound lack of energy. Fatigue is one of the most common side effects of radiation therapy. Patients are not restricted from normal activity during radiation therapy; however, they should balance normal activity with periods of rest. Fatigue is typically more severe 2-4 hours after treatment. The feeling of fatigue should wear off several weeks after the completion of radiation therapy. The following suggestions may help you manage fatigue resulting from radiation therapy:

  • Limit your activities, if possible.
  • Exercise each day to maintain your strength.
  • Prepare meals ahead of time and freeze them.
  • Use convenience foods that are ready to eat.
  • Accept offers of help from friends and relatives.
  • Drink three quarts of fluid each day to avoid the build-up of cellular waste products.
  • Increase rest by getting more sleep at night and taking naps during the day.
  • Try to eat even when you are tired. Sometimes a little food will increase energy.