Side effects of brachytherapy

Brachytherapy causes similar side effects to external radiotherapy

It’s common to feel mild soreness, and to have some bruising and discoloration between the legs for a few days after the procedure. Your doctor can prescribe painkillers to relieve this.

Erection problems 

Brachytherapy can cause erection problems some years after the treatment. The risk is the same as with external radiotherapy. But your risk may be higher if you’re having external beam radiotherapy or hormonal therapy as well as brachytherapy. Ask your specialist if they are able to give you an idea of your likely risk of erection problems. 


Brachytherapy may cause infertility in some men. 

Effects on the bowel 

Brachytherapy may be less likely to affect the bowel than external radiotherapy. But if it is given with external radiotherapy, the side effects will be the same.

Effects on the bladder 

  • Blood in your urine
    You may notice some blood in your urine and semen for a few weeks. This is normal, but if it becomes severe or you have large clots, let your doctor know immediately. Drink plenty of water to help prevent blood clots and to flush the bladder.
  • Unable to pass urine
    The procedure may cause some men to have difficulty passing urine due to swelling. You may have a catheter put in either during or after the procedure to help manage this. It will be removed when the tissues have healed. Sometimes difficulties passing urine may develop due to narrowing of the urethra. This can happen weeks or months after the procedure.
  • Urine leakage
    This may affect a small number of men. We have more information about managing incontinence.
  • Other problems
    Some men find they have pain or discomfort when they pass urine, that they need to pass urine more often, or they have a weaker urine stream. This usually happens with permanent seed therapy and is due to the radiation from the seeds in the prostate. It improves over 3–12 months as the seeds lose some of their radioactivity. Drink plenty of fluids and avoid caffeine to help reduce these effects.

Most men will be able to return to their normal activities 1–2 weeks after treatment. But your recovery will take longer if you have external beam radiotherapy as well. For example, after high dose rate brachytherapy.

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