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A quick guide to what's on this page

External radiotherapy for prostate cancer

This treatment uses a high dose of radiation just to the area of the prostate gland. You can have this treatment if your prostate cancer is only in the prostate gland or has just broken through the prostate capsule. If it has spread any further, this treatment is not likely to cure it.

How you have the treatment

You usually have a course of daily treatments lasting about 6 to 7 weeks. During that time you go to the hospital radiotherapy department each day from Monday to Friday. The treatment only takes a few minutes each time.

Side effects

Some side effects usually come on gradually as you go through your course of treatment. They include sore skin in the treatment area, irritation of the bladder, needing to pass urine more often, diarrhoea, and tiredness.

Your side effects may last for several weeks after your treatment has finished. The tiredness can last for some months.

Long term side effects

Some men have long term problems after this type of treatment. Unfortunately, doctors cannot tell who will be affected. Many men have problems getting an erection. Some men have problems passing urine. Some have a straining feeling in the back passage, called proctitis. Radiotherapy for prostate cancer can also increase the risk of cancer of the back passage (rectum). 


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How external radiotherapy for prostate cancer works

External radiotherapy treatment uses a high dose of radiation just to the area of the prostate gland. Your treatment team will make sure the whole of your prostate gland is treated as well as an area of 1 to 2 centimetres around it. This is to make sure that any cancer cells a little way away from the main tumour are treated. These cells are called microscopic spread. They are too small to be seen on scans, but if they are not treated the prostate cancer is more likely to come back in the future.

You can have external radiotherapy treatment if your prostate cancer is between stage T1 and T3. This means that the cancer can have spread through the covering of the prostate gland (the capsule). But it must not have spread any further. If it has spread further, this treatment is not likely to cure it. And because of the side effects, it may not be the best treatment for you.


How and where you have radiotherapy

You have to travel to hospital for radiotherapy treatment. You have it in the radiotherapy outpatient department. The radiotherapy dose is split into a course of small treatments. If you were to have the total dose in one go, it would harm normal body tissues too much. So you have a small dose each day over a number of weeks. Doctors call each dose a fraction.

External radiotherapy treatment can be given in different ways. But you usually have it once a day, for 5 days each week, from Monday to Friday. It takes about 6 to 7 weeks.


Planning your treatment

Radiotherapy is specialist treatment and your treatment team will plan it very carefully and individually for you. At your first visit you may lie under a CT scanner. You may also have an MRI scan. The doctor uses the scans to plan exactly where to give the treatment.

During planning you have one or more pinprick tattoos made on your skin. The radiographers use these to line up the radiotherapy machine accurately every time you have treatment. They may also draw marks on your body with a felt tip pen. Try not to wash them off. They will fade, though. So tell your radiographer if they fade and they will draw them in again.


Having radiotherapy

Each treatment session only takes a few minutes. The radiographers will help to position you on the radiotherapy couch and make sure that you are comfortable.

Picture of simulator machine

The staff will leave you alone for the minute or two that the machine is switched on. But they will be able to hear you through an intercom or video link, so you can call if you need them. The treatment doesn't hurt. You will not be able to feel it at all. You must lie very still for the few minutes it takes to treat you.

You might find it helpful to look at our page about external radiotherapy. It has a 3D photograph of a radiotherapy treatment room and a video of a patient having radiotherapy.

Having external radiotherapy does not make you radioactive. It is perfectly safe to be with other people, including children, throughout your treatment course.


Temporary side effects

You will probably have some side effects from radiotherapy treatment. The most common ones are

  • An inflamed bladder, making you want to pass urine very often
  • An inflamed bowel, causing diarrhoea
  • Tiredness
  • Sore skin in the area of the prostate and around the back passage
  • Loss of pubic hair

Your side effects may last for several weeks after your treatment has finished. Tiredness can last for some months afterwards. There is detailed information about coping with side effects in this section.


Long term side effects

External radiotherapy can have side effects that last for longer than a few weeks. For most men, these symptoms settle down gradually but for some they are permanent. Unfortunately, your doctor cannot tell before you are treated whether you are likely to have permanent side effects. 

Possible permanent side effects include

Bowel problems

There are two types of bowel problems you may have. Proctitis is a straining feeling in the back passage. Some men also develop problems with frequent, loose bowel movements.  

Problems getting an erection (impotence)

Not being able to get an erection is a permanent side effect for many men treated with prostate radiotherapy. The risk of erection problems varies in different studies but can be from 40 to 70%. If you are having hormone treatment as well as radiotherapy, the risk of erection problems is higher. We have information about ways of managing erection problems on our page about sex and cancer in men.

Problems passing urine

You may also have problems with passing urine. Some men develop a narrowing of the tube that carries urine from the bladder.

An increased risk of rectal cancer

External beam radiotherapy for prostate cancer can also increase the risk of developing cancer of the back passage (rectum) but the risk is still small.


More information about prostate cancer radiotherapy

This section of the website has information about the different types of prostate cancer radiotherapy. There is also detailed information about managing radiotherapy side effects.

We have information about the other treatments for prostate cancer and their possible side effects. You can also phone the Cancer Research UK nurses on freephone 0808 800 4040, from 9am to 5pm, Monday to Friday. They will be happy to answer any questions. 

UK Prostate Link can direct you to information about external radiotherapy treatment for prostate cancer. Our prostate cancer organisations page gives details of other people who can give information about prostate cancer treatments. Some organisations can put you in touch with a cancer support group.

Our prostate cancer reading list has information about books, leaflets and other resources discussing treatments.

If you want to find people to share experiences with online, you could use Cancer Chat, our online forum.

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Updated: 24 February 2014