External beam radiotherapy uses high energy X-ray beams to treat prostate cancer. The X-ray beams are directed at the prostate gland from outside the body. They damage cancer cells and stop them growing.

Radiotherapy treats the whole prostate, and sometimes the area around it. The treatment is painless but it can cause side effects.

You may be able to have radiotherapy if your cancer is contained inside the prostate (localised prostate cancer). Radiotherapy may also be suitable for you if your cancer has spread to the area just outside the prostate (locally advanced prostate cancer).

Radiotherapy can also be used after surgery if your PSA level starts to rise or if tests suggest that not all the cancer was removed with surgery.

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What types of external beam radiotherapy are there?

There are two types of external beam radiotherapy, 3-dimensional conformal radiotherapy (3D-CRT) and intensity modulated radiotherapy (IMRT).

You may also hear about image guided radiotherapy (IGRT). This is used as part of all radiotherapy treatments. Your radiographer will take an X-ray or a scan just before your treatment to pinpoint the exact position of your prostate, as well as its size and shape.

At some hospitals, you may have three to four gold seeds, called fiducial markers, put inside your prostate. These are about the size of a grain of rice. The seeds show up on scans and help the radiographer see the exact position of the prostate.

3D conformal radiotherapy (3D-CRT)
With 3D-CRT, the radiation beams match the shape of the prostate as closely as possible. This helps to avoid damaging the healthy tissue surrounding it, reducing the risk of side effects.

Intensity modulated radiotherapy (IMRT)
With IMRT, the radiation beams are matched precisely to the size, shape and position of the prostate. The strength of the radiation beams can also be controlled so that different areas get a different dose. This means a higher dose of radiation can be given to the prostate, without causing too much damage to the surrounding tissue.

The risk of side effects is usually lower with IMRT than with 3D-CRT.

Some hospitals offer 3D-CRT and others IMRT. Ask your doctor or radiographer which type of radiotherapy you’re being offered.

What are the advantages and disadvantages?

What may be an advantage for one person might not be for someone else. Talk to your doctor, nurse or radiographer before deciding whether to have radiotherapy – they’ll be able to help you decide if it’s right for you.


  • Many men are able to carry on with their normal day-to-day activities during treatment.
  • Radiotherapy can be an option even if you’re not fit or well enough for surgery.
  • Radiotherapy is painless, but you might find the treatment position slightly uncomfortable.
  • Daily sessions only last 10 to 20 minutes, including the time it takes to get you into position.
  • You don’t need to stay in hospital.


  • You will need to go to hospital five days a week for several weeks. This might be difficult if you need to travel far.
  • You may get side effects such as bowel, urinary and erection problems, as well as tiredness and fatigue. 
  • It may be some time before you know whether the treatment has been successful.
  • If you have radiotherapy as your first treatment and your cancer comes back or spreads, surgery might not be possible.

What does treatment involve?

You may have hormone therapy for three to six months before you begin radiotherapy. This shrinks the prostate and makes the cancer easier to treat. Men who have a higher risk of their cancer spreading may continue to have hormone therapy for up to three years after radiotherapy.

A week or two before starting radiotherapy you will usually have a planning session, where you will have scans of your prostate. This is to make sure the treatment is accurate and the surrounding areas don’t get more radiation than necessary. In most hospitals, three very small permanent marks (tiny tattoos) are made on your skin. This helps the radiographers get you into the right position.

You will have one treatment (known as a fraction) at the hospital five days a week with a rest over the weekend. You can go home after each treatment.

Radiotherapy usually continues for seven to eight weeks. Some hospitals may offer a shorter course of about four weeks, with higher doses at each session – but a slightly lower total dose.

At the start of each session, the radiographer will help you get into the right position – using the marks made on your body as a guide.

The machine will take an X-ray or a scan to make sure that you are in exactly the right position. The treatment then starts and the machine moves around your body. It doesn’t touch you and you won’t feel anything. You’ll need to keep very still, but the treatment only takes a few minutes. The whole session lasts 10 to 20 minutes, including the time it takes to get you into position.

It’s safe for you to be around other people, including children and pregnant women, during your radiotherapy. The radiation doesn’t stay in your body so you won’t give off any radiation.

Eating and drinking
Your prostate sits close to your bladder and bowel. Most hospitals will tell you how full or empty your bladder and bowel should be during treatment. This helps the radiographers to make sure they treat the right area each time and can also help reduce side effects.

Some hospitals will give you advice about your diet, and you may be given a laxative to help empty your bowels. You will usually be asked to drink water while you’re waiting for treatment so that your bladder is comfortably full.

Anti-oxidants and radiotherapy
Some people take anti-oxidants such as vitamin C and E, lycopene and selenium for their cancer – although there’s no clear evidence that they help. Some research suggests that anti-oxidants might protect the cancer cells from radiotherapy, and make radiotherapy less effective. Speak to your doctor, nurse or radiographer before taking anti-oxidants.

What happens after radiotherapy?

You will have regular check-ups after your radiotherapy.

  • Your first check-up is usually between six weeks and three months after treatment.
  • You may then have a check-up every six months.
  • After two years, you might have a check-up once a year.

Check with your doctor or nurse how often you will have check-ups.

PSA test
You will usually have a PSA test a week before your check-up. PSA tests are a very effective way of checking how well your treatment has worked.

After radiotherapy, your PSA should start to drop. Some PSA will still show up in tests because healthy prostate tissue will continue to produce PSA. How quickly your PSA level drops, and how low it falls, will depend on whether you had hormone therapy alongside radiotherapy. If you had radiotherapy on its own, it may take up to two years for your PSA level to fall to its lowest level (nadir). If you had hormone therapy as well as radiotherapy, your PSA level may fall more quickly.

You may see a rise and fall in your PSA level around one to two years after treatment. This is called ‘PSA bounce’. It is normal, and doesn’t mean your cancer has come back. A sign that your cancer may have come back is if your PSA level has risen by 2ng/ml or more above its lowest level, or if it has risen for three or four PSA tests in a row.

If your PSA level does rise, your doctor may check your PSA level for at least six months before deciding on further treatment.

Treatment options after radiotherapy
If the cancer does come back, there are further treatments that you may be able to have:

Surgery is very rarely an option because radiotherapy makes it difficult to remove the prostate.

What are the side effects?

Like all treatments, radiotherapy can cause side effects. These will affect each man differently, and you might not get all of the possible side effects.

Side effects happen when the healthy tissue near the prostate is damaged by radiotherapy. Most healthy cells recover so side effects usually only last a few weeks or months. But some side effects can start months or years after treatment. These may be similar to the side effects you had during or soon after radiotherapy and can last a long time.

If you have hormone therapy as well as radiotherapy, you may also get side effects from the hormone therapy.

Urinary problems
Radiotherapy can irritate the lining of the bladder and the urethra (the tube men urinate through) and cause urinary problems. These can include needing to urinate urgently and more often and, sometimes, blood in the urine.

Bowel problems
Radiotherapy can irritate the lining of the bowel (called proctitis) and cause bowel problems. Symptoms vary from man to man. Some will notice a slight change in their bowel habits rather than a problem.

Bowel problems often improve once treatment has finished, but some men will find that their bowel habits change permanently. Bowel problems can develop months or years after treatment.

Bowel problems and anal sex
If you’re gay, bisexual or a man who has sex with men, and are the receptive partner (‘bottom’) during anal sex, then bowel problems after radiotherapy may be a particular issue. Read our information for gay and bisexual men.

Tiredness and fatigue
The effects of radiation on your body can leave you feeling very tired, especially towards the end of your treatment.

Fatigue is extreme tiredness or exhaustion that can affect your everyday life. It might improve after your treatment but some men find it lasts longer.

There are things you can do to help manage fatigue. Our telephone programme fatigue support is designed to help you deal with fatigue. If you’re still working, read about managing fatigue at work.

Sexual problems
You might get erection problems. It can take up to two years for erection problems to fully appear.

You may not produce any semen after radiotherapy. You may have a dry orgasm where you feel the sensation of orgasm but don’t ejaculate. This may feel different to the orgasms you were used to. If you might want to have children in the future, you might want to store your sperm before you start radiotherapy, so that you can use it later for fertility treatment. Ask your doctor, nurse or radiographer about sperm storage. 

There is a very small chance that radiotherapy could affect any children you might conceive during treatment. You may wish to use contraception during and after treatment if there is a chance of your partner becoming pregnant. Ask your doctor, nurse or radiographer for advice.

Other problems
You may get other problems during or many years after your treatment. These can include the following.

  • Skin irritation – during treatment, the skin between your legs may become sore but this is rare.
  • Hair loss – some of your pubic hair might fall out but this usually grows back after radiotherapy.
  • Lymphoedema– if your lymph nodes are treated, there is a slight chance that fluid might build up in your tissues. It usually affects the legs, but it can affect other areas, including the penis or testicles. It can happen months or even years after radiotherapy.
  • Hip and bone problems – radiotherapy can damage the bone cells and the blood supply to the bones near the prostate. This can cause pain, and hip and bone problems later in life.
  • Other cancers – radiotherapy could increase your risk of bladder or bowel cancer. This is very rare. It would take at least 5 to 15 years for a second cancer to appear.

Talk to your doctor or nurse about your own risk of long term side effects. You might be more likely to get them if:

  • you’re older
  • you have diabetes
  • you’ve had bowel or prostate surgery in the past
  • you’ve had bladder, bowel or erection problems in the past.

Questions to ask your doctor, nurse or radiographer

  • What type of radiotherapy will I have?
  • How many sessions will I need?
  • What are the possible side effects and how long will they last?
  • Will I be able to carry on with my day-to-day life during treatment?
  • Will I have hormone therapy and will this carry on after radiotherapy?
  • How will we know if radiotherapy has worked?
  • If the radiotherapy doesn’t work, which other treatments can I have?
  • Who should I contact if I have any questions?
  • What support is there to help manage long term side effects?


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