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Side effects of prostate cancer radiotherapy

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Side effects of prostate cancer radiotherapy

Side effects of radiotherapy for prostate cancer can be short term or long term. 

Short term effects

Short term side effects usually start during your course of treatment and go away soon after it is finished. The effects are different for external radiotherapy and internal radiotherapy (brachytherapy).

Side effects of external radiotherapy can be diarrhoea, needing to pass urine often due to bladder inflammation, pain passing urine, and sore skin in the treatment area.

With internal radiotherapy, the side effects mentioned above occur less often. But you may have difficulty passing urine. Or you may not be able to pass urine at all. This is not very common. But if you can't pass urine, you will need to have a tube (catheter) put into your bladder to drain the urine. These side effects usually disappear within a few weeks.

Long term effects

Long term side effects can begin some months or years after treatment. They may gradually get better or may be permanent. Your doctor can’t tell ahead of time whether you will have long term side effects or not. The most common long term side effect is a straining feeling in the back passage called proctitis. 

Up to 7 out of every 10 men (70%) will no longer be able to get an erection after radiotherapy treatment for prostate cancer. This side effect is less likely to occur after internal radiotherapy (brachytherapy) than external radiotherapy. It is more common in older men.

A narrowing of the tube from the bladder to the penis (the urethra) can cause difficulty passing urine. This occurs most often after internal radiotherapy.


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Short term side effects

The main short term side effects from external radiotherapy to the prostate are

  • Bladder inflammation
  • Diarrhoea
  • Sore skin in the genital area
  • Loss of pubic hair

Internal radiotherapy (brachytherapy) causes similar short term side effects. You may also have some difficulty passing urine. Or you may not be able to pass urine at all. This happens in up to 15 out of 100 men (15%). If it happens to you, you must contact your doctor straight away. 

You will need to have a tube (catheter) put into your bladder to drain it. These side effects usually disappear within a few weeks. Other much less common side effects include blood in the urine or semen. Swelling of the tissues in the back passage (rectum) can also cause constipation.

Bladder inflammation

You may find that you have to pass urine more often than usual. And you may have a burning feeling when you do. This is called radiation cystitis. The radiation has inflamed the lining of your bladder. This may get worse as you go through your course of treatment. But it should get better within a few weeks of finishing. 

It will help if you drink plenty of fluids. Some people think particular drinks can help, such as cranberry juice but research studies have not found that it helps. 

You may find that some drinks can make the bladder inflammation worse, such as tea and coffee. You can experiment for yourself and see what works for you. You should avoid potassium citrate, an old fashioned remedy for cystitis. You may hear it called mist pot cit for short. This drug can be very dangerous if taken in large amounts.

These effects usually disappear within a few weeks of finishing your treatment.


Diarrhoea is a common side effect of external radiotherapy. It is caused by radiation irritating the lining of your bowel. 

Your doctor can prescribe tablets to help slow down your bowel. This should help reduce the number of times you have diarrhoea. During the few weeks following your treatment, the diarrhoea should gradually get better.

Sore skin in the genital area

Sore skin in the treatment area is not as common as it was because radiotherapy techniques have improved. But the skin between the legs is delicate and can get very sore towards the end of your treatment. 

You must tell the nurse or radiographer at your treatment centre if you notice reddening or soreness. If your skin becomes very sore, they can prescribe creams to help.

Loss of pubic hair

Radiotherapy causes hair loss in the treatment area. Sometimes the hair loss is patchy, rather than complete hair loss. The hair can grow back, but not always completely. It may take several months for the hair to grow back.


Long term side effects

There are some possible long term side effects from radiotherapy to the prostate. These are

  • Erection problems (impotence)
  • Problems passing urine
  • Frequent, loose bowel movements
  • Inflammation of the back passage (proctitis)

Your doctor will not be able to tell before your treatment whether any of the permanent side effects will happen to you. But some side effects are more likely in some people. The likelihood of long term side effects will also vary depending on the type of radiotherapy you have. 

You may have a higher risk of side effects if you have a course of external radiotherapy as well as internal radiotherapy (brachytherapy).

Erection problems (impotence)

Radiotherapy can damage the nerves that control getting an erection. Different studies give different statistics but from 4 to 7 out of every 10 men (40 to 70%) will no longer be able to get or keep an erection after external radiotherapy treatment for prostate cancer. If you have hormone therapy either before or after your radiotherapy, this further increases the risk of erection problems.

Whether you have problems getting and keeping an erection after internal radiotherapy (brachytherapy) depends on your age and whether you have other health conditions. If you are under 65 when you are treated, impotence is less likely than if you are over 70.

Brachytherapy studies show that between 14% to 45% of men have erection problems after treatment.

If erection problems occur, tell your doctor as soon as possible. Early treatment with medicines such as sildenafil (Viagra) or apomorphine hydrochloride can help to reduce erection problems.

Problems passing urine

Radiotherapy to the prostate can cause difficulty passing urine. This can happen with internal or external treatment. The treatment causes a narrowing of the tube from the bladder to the penis. The narrowing is called a stricture. It can make it difficult for you to pass urine and in an extreme case, you may not be able to pass urine at all. You can have treatment for this. 

The narrow area is stretched under anaesthetic during a short operation. Between 5 and 8 out of every 100 men (5 to 8%) need this operation. Some men may need more than one operation.

Leakage of urine (urinary incontinence) is rare nowadays. But it is more likely if you have previously had a TURP operation. Brachytherapy research has reported that between 1 and 14 men out of every 100 treated (1 to 14%) have some problem with leaking urine within 3 to 5 years of the treatment.

Radiation damage can cause slight leaking, or a more severe problem, with complete lack of control of urine. But this is very rare. If urine leakage becomes a long term problem your doctor can refer you to a specialist incontinence clinic. Staff there can help you with muscle exercises, bladder training and medicines.

Frequent or loose bowel movements

Your bowel movements may continue to become looser or more frequent than they were before your treatment. This can come and go for some men.  

You may need to take anti diarrhoea medicines at times. Bulking agents, such as Fybogel may also help. You may find that you have to avoid high fibre foods. Although we normally think that a high fibre diet is the most healthy, it may not be good for you if you have chronic diarrhoea. Some men find it best to avoid high fibre vegetables, beans and pulses (such as lentils).

If you have ongoing problems with frequent bowel movements or bleeding, let your doctor know. They can refer you to a specialist team. The team includes cancer doctors, digestive system specialists, bowel surgeons, dietitians and specialist nurses. They can carry out tests to see what is causing the problem and then give treatment to control it.

Inflammation of the back passage (proctitis)

Inflammation of the back passage (rectum) is the most common long term side effect. Proctitis can cause a feeling of wanting to strain whether or not you actually need to pass a bowel movement, and bleeding from your back passage. You may also have a slimy mucous discharge from your rectum. 

Some men only have the straining feeling. Some only have bleeding. Bleeding is usually slight, but can be more severe for some men. Talk to your cancer specialist if you have proctitis. Treatments such as steroid suppositories may be able to reduce the inflammation. 


More information about coping with side effects

Find out about

External radiotherapy for prostate cancer

Internal radiotherapy for prostate cancer

Hormone therapy

Sex and cancer for men

TURP operation

Bowel problems and how to manage them

Coping physically with cancer

Prostate cancer organisations

Prostate cancer reading list

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Updated: 25 February 2014