Side effects of prostate cancer radiotherapy

Radiotherapy to the prostate can cause some side effects, such as loose or watery poo (diarrhoea) and passing urine more often.  

Side effects tend to start a week or 2 after the radiotherapy begins. They gradually get worse during the treatment and for a couple of weeks after the treatment ends. But they usually begin to improve after around 2 weeks or so after treatment finishes

Everyone is different and the side effects vary from person to person. You may not have all of the effects mentioned.

Tiredness and weakness

You might feel tired during your treatment. It tends to get worse as the treatment goes on. You might also feel weak and lack energy. Rest when you need to.

Tiredness can carry on for some weeks after the treatment has ended but it usually improves gradually.

Various things can help you to reduce tiredness and cope with it, such as exercise. Some research has shown that taking gentle exercise can give you more energy. It's important to balance exercise with resting.

Sore skin in the treatment area

Your skin in the treatment area might get sore, or redden or darken. Following these tips can help with this: 

  • Wear loose fitting underwear and clothes. Natural fibres can be more comfortable than man-made fibres.
  • Gently wash the area each day. Use mild, unperfumed soap and warm or cool water. Try baby soap or liquid baby wash but check with the radiotherapy staff first.
  • Gently pat the skin dry with a soft towel. Rubbing the skin can make it sore.
  • Don't use perfumed lotions on the area. Use only creams or dressings recommended by your specialist or radiographer.
  • Don't use talcum powder because it can contain tiny metal particles. The particles can make the soreness worse.
Tell the nurse or radiographer at your treatment centre if you notice reddening or soreness. 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. The hair can grow back, but not always fully. It might take several months.

Problems passing urine

You may feel:  

  • as if you want to pass urine all the time (but when you go, there isn't much there)
  • as if you have a bladder infection (cystitis)
  • a burning pain when you do pass urine
  • a weak flow of urine 

Try to drink plenty of water. Many people think that drinking cranberry juice can be helpful with bladder problems. But this isn't the case for bladder problems caused by radiation. 

Your bladder inflammation should settle down a few weeks after your treatment is over.  

Tell your doctor if you have any pain when passing urine. It could be a sign that you have an infection. They might arrange for you to do a urine test (Mid Stream Urine). You may need antibiotic treatment.

Loose or watery poo (diarrhoea)

Tell your doctor, nurse or radiographer if you have diarrhoea. They can prescribe medicine to help you. 

Drink plenty of fluids. This helps to keep you hydrated. 

Ask your nurse about soothing creams to apply around your back passage (rectum). The skin in that area can get very sore and even break if you have severe diarrhoea.

Possible long term side effects

Most side effects gradually go away in the weeks or months after treatment. But some side effects can continue or might start some months or years later. This includes problems getting an erection.  

Last reviewed: 
16 Jun 2022
Next review due: 
16 Jun 2025
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