Long term side effects of brachytherapy for prostate cancer

Brachytherapy Open a glossary item for prostate cancer can cause some long term side effects. These include problems passing urine and difficulty getting an erection. 

Everyone is different and the side effects vary from person to person. You may not have all of the effects mentioned. Tell your doctor or nurse if you have any of these problems. They can help you to find ways of controlling the effects. 

About side effects

Before treatment, your doctor will explain the risk of you getting side effects. But they won’t be able to tell you whether any of these side effects will definitely happen to you. Some side effects are more likely in some people.

Your risk of side effects is higher if you have brachytherapy as well as external radiotherapy.

Problems passing urine

You might have problems passing urine after the radiotherapy ends. It might be more difficult to pass urine at first. And then it might gradually get easier over some months or years. This is due to the treatment causing a narrowing of the urethra Open a glossary item. The narrowing is called a urethral stricture.

Tell your doctor if you find it harder to pass urine.

You can have an operation to stretch it. This short operation is called urethral dilatation. They might slide a thin rod into the urethra to widen it. Or they may use a thin flexible tube with a light and camera on the end. They can see the narrowed area and put a tiny knife down the tube to cut away tissue and open up the urethra. You have these operations under local anaesthetic Open a glossary item or general anaesthetic Open a glossary item.

You might need to have this operation repeated if the urethra gets narrower again.

A small number of men find they can’t pass urine at all. This is called urine retention. You need to go to your local accident and emergency (A and E) department if:

  • your tummy (abdomen) feels swollen and uncomfortable
  • you can’t pass urine

The staff there will put in a catheter Open a glossary item to drain your bladder.

Leakage of urine

You may have some problems with leaking urine after treatment with brachytherapy. 

There is specialist incontinence clinic if urine leakage becomes a long term problem. Your nurse or doctor can refer you. The clinic can help you with muscle exercises, bladder training and medicines.

Some men find that they can’t control their urine at all. This is very uncommon. If it happens you need to have a tube called a catheter into your bladder. The tube drains the urine into a bag.

Erection problems (impotence)

Radiotherapy can damage the nerves that control getting an erection.

Whether you have problems getting and keeping an erection depends on several factors. These include:

  • your age (impotence is less likely if you are under 65)

  • whether you have other health conditions

  • whether you had erection problems before the treatment

  • if you have hormone therapy before or after the radiotherapy

  • whether you have internal radiotherapy as well as external radiotherapy

Tell your doctor or specialist nurse as soon as possible if you have erection problems. Early treatment with medicines such as sildenafil (Viagra) might help you to get and keep erections. If you continue to have problems, they can refer you to a specialist to help with this. 

Problems with your bowels and back passage

Your bowel movements might be looser or more frequent than before your treatment. You might need to take anti diarrhoea medicines, such as loperamide (Imodium). Bulking agents, such as Fybogel might also help. 

Inflammation of the back passage (rectum) is called proctitis. This is a possible long term side effect. Proctitis can cause:

  • a feeling of wanting to strain whether or not you actually need to pass a bowel movement
  • bleeding from your rectum
  • a slimy mucous discharge from your rectum

Talk to your doctor or specialist nurse if you have any of these side effects. They will be able to refer you to a specialist team to check the cause. They can help you to find ways of controlling the effects. 

Cancer of the bladder or lower bowel

A small number of men develop bladder cancer or cancer of the lower bowel (rectum) after radiotherapy for prostate cancer. This can happen many years after treatment.

It is important that you contact your GP if you notice blood in the urine or poo or a change in your bowel habits.

Coping and support for you and your family

Coping with the side effects of prostate cancer radiotherapy can be difficult. There are things you can do, and people who can help you and your family to cope. 

  • Prostate cancer: diagnosis and management
    National Institute for Health and Care Excellence (NICE), 2019. Last updated December 2021

  • Long-Term Efficacy and Toxicity of Low-Dose-Rate¹²⁵I Prostate Brachytherapy as Monotherapy in Low-, Intermediate-, and High-Risk Prostate Cancer
    JA Kittel and others
    International Journal of radiation oncology, biology, physics, 2015. Vol 92, Issue 4. Pages 884-894

  • Brachytherapy for low-risk or favorable intermediate-risk, clinically localized prostate cancer
    M Roach and S DiBiase
    UpToDate, accessed July 2025

  • Prostate Testing for Cancer and Treatment (ProtecT) Study Group. Functional and quality of life outcomes of localised prostate cancer treatments (Prostate Testing for Cancer and Treatment [ProtecT] study)
    J Lane and others
    British Journal of Urology International, 2022. Volume 130, Issue 3, Pages 370 - 380

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in if you need additional references for this information.

Last reviewed: 
02 Jul 2025
Next review due: 
02 Jul 2028

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