External beam radiotherapy for early prostate cancer

Radiotherapy uses high-energy X-rays to kill cancer cells. When radiotherapy is given externally it is called external beam radiotherapy. In this case a beam of radiation is aimed at your prostate gland from a machine called a linear accelerator. These X-rays damage the cancer cells, prevent them from growing and cause the cells to die.

Although normal cells are also affected they can repair themselves. The treatment is suitable if your prostate cancer is found only within your prostate gland or has spread just outside it. The aim of radiotherapy is to fully get rid of your prostate cancer.

External beam radiotherapy 

There are two types of external beam radiotherapy available:

  • Conformal radiotherapy: This is the most common type of radiotherapy. The machine directs the beam to fit the size and shape of your prostate gland.
  • Intensity-modulated radiotherapy (IMRT): This gives a more precise form of radiation. The beam of radiation is adjusted to give different doses to different parts of your prostate.

It is a newer form of radiotherapy available in only some treatment centres in Ireland. Both types of external-beam radiotherapy try to reduce the amount of radiation given to normal tissues close to your prostate gland. This helps to reduce the risk of side-effects. Your radiation oncologist will discuss which type of radiotherapy is suitable for you. 

Radiotherapy in combination with other treatments

Radiotherapy is sometimes used on its own or together with hormone therapy. The hormone therapy is given to reduce the size of your prostate gland and make the cancer easier to treat. It is common to have hormone therapy for some months before radiotherapy and to continue it during treatment and for some time afterwards.

The length of time you need to take hormone therapy varies. It will all depend on the degree of risk of your cancer. It may last 6 months or for some men 2–3 years. You can ask your radiation oncologist for how long you need to take the hormone treatment.

What does the treatment involve?

If a course of external beam radiotherapy is needed it usually lasts for 7-9 weeks. This means going to the radiotherapy unit 5 days a week, with a break at weekends. The treatment itself only takes a few minutes and does not hurt.


Some preparation is needed before the actual radiotherapy can be given. Before treatment, you will visit the hospital for planning scans that use a machine called a simulator. This helps your doctors to work out exactly where to aim the X-rays.

They will mark your skin so that the beam goes to the same area each time you get radiotherapy. You might also have gold markers called fiducials put into your prostate to make sure the radiotherapy targets the right area. These may be put into your prostate gland under local anaesthetic during the planning visit. 

What are fiducials?

Fiducials are small gold seeds which may be inserted during the planning session for radiotherapy.

The seeds are inserted using the same method as a prostate biopsy, by placing hollow gold needles through the rectum (back passage) and moving a fiducial through each needle. The fiducials show up on scans and help the radiographer to locate the exact position of the prostate each day before you receive treatment.

This means the radiation can be delivered to the prostate with precision and accuracy. This may reduce injury to the surrounding areas around the prostate. There are a few rare side-effects with inserting the gold seeds. These may include infection, temporary local pain and blood in the urine, stool and semen.

Special diet and fluids

It is important that your prostate gland is in the same position every time you have your treatment. The exact position of your prostate can be affected by having a full bladder or a full bowel.To make sure your prostate is in the same position each time, the staff in the radiotherapy unit may ask you to follow a special diet, drink some water just before your treatment, or give you an enema.

This is a fluid solution gently inserted in through your back passage which then causes you to clear your bowels beforehand.

Having treatment

Before you have each treatment, the staff will help you into the right position on the radiotherapy table. They will use the marks on your body to make sure that the treatment is given to the right spot each time.

Before the treatment starts, the staff will leave the room. They can see and hear you at all times and you can talk to them. During the treatment the machine will move around your body, but it does not touch you and you will not feel anything.

After treatment

The radiation does not stay in your body after the treatment, so it is perfectly safe to be around other people at all times afterwards.Treatment affects people in different ways. You might be able to continue your normal activities, such as work or social activities, or you might feel that you need more rest than usual.

Side-effects of external beam radiotherapy

Side-effects occur when the normal healthy cells near the treated area are exposed to the beam of radiation. Some side-effects appear during the treatment while others can develop afterwards.

The most common side-effects are those that develop during or shortly after your treatment. Not all men will get all of the side effects. But there is no way of knowing which of them you will get or how much trouble they will cause you.

During your treatment, your radiation therapists can discuss side-effects and advise you on how best to manage them.

Some side-effects may include:

Urinary problems

During radiotherapy your bladder may become irritated. This can make you pass urine more often, during the day and at night. It can also cause a burning feeling when you pass urine. Sometimes drinking too much tea, coffee, cola or alcohol can make these problems worse. If this happens, reduce your intake of these drinks for a time and drink more water, juices or soft drinks. You may notice a trace of blood in your urine too. If you have problems passing urine or pass blood, discuss it with your doctor, nurse or radiation therapist. Urinary problems usually start to settle down some weeks after your treatment has finished. But for some men they continue long term. On your way home from each treatment you may need to stop to pass urine, especially if you are asked to drink water before each treatment. Your bladder might be permanently affected by radiotherapy. This happens with a very small number of men. As well as the short-term symptoms, you mightdevelop a narrowing of your urethra (water pipe). This can make it difficult to pass urine and will need to be treated with surgery. Sometimes the blood vessels in your bladder can become more fragile after radiotherapy. This can take many months or years to happen and causes some blood to appear in your urine. If you notice any bleeding, tell your doctor so that tests can be done and proper treatment given. Rarely, radiotherapy can cause leakage of urine due to damage to the nerves that control your bladder muscles. But this is unlikely unless you have had prostate surgery as well. If this happens, discuss it with your doctor or nurse. For more information visit our section Urinary symptoms, catheters and prostate cancer treatment. 

Bowel problems

You might develop diarrhoea during treatment. This is because your prostate gland is very close to your back passage (rectum). Passing watery bowel motions more than twice a day is known as diarrhoea. You may also have cramping tummy pain and pass more wind and mucus.

You might also notice that you need to get to the toilet more quickly. If you develop diarrhoea, drink lots of fluids to replace the fluids you are losing. Let your doctor or radiation therapist know if you have diarrhoea. There is medication that can stop this side-effect. 

Including too much fibre in your diet during radiotherapy may make the diarrhoea worse for some men. In this situation eating a more low fibre diet may be helpful but it is important to talk to your radiation therapist, doctor or nurse before making any changes to your normal diet if you are experiencing symptoms.

Low fibre foods include potatoes (peeled) white rice and pasta. It might also help to avoid gassy foods like beans, beer, fizzy drinks and green leafy vegetables like cabbage/ cauliflower/sprouts.

Wholegrain bread, whole grains cereals and fresh fruit are also high in fibre and should be avoided if you are following a low-fibre diet. Eat and drink slowly and chew your food more slowly. 

Radiotherapy could also cause you to have more difficulty opening your bowels and you may become constipated.  You might feel like you have not emptied your bowel properly after going to the toilet.

Your doctor and nurse will help you find ways to manage your bowel symptoms during your treatment. Again, these symptoms usually start to settle down a short time after your treatment has stopped. 

Before your treatment starts it is important to tell your doctor if you have had other bowel problems in the past, as this may increase your chance of developing bowel problems during and after the radiotherapy treatment.

Your radiation therapist or nurse may give you a specific dietary advice sheet to follow while undergoing the radiation treatment. It may also be possible to speak with the dietician in the hospital for further advice if you need it.

In some cases bowel problems might carry on. Or they might develop years after treatment and you find that your bowel habits change permanently. Bowel motions may be more urgent and frequent after radiotherapy.

This may mean you open your bowels a little more often than you did before your treatment. Or it may mean a bigger change that affects your everyday life. Tell your doctor about any bowel problems that you have, as there are treatments that can help.

The blood vessels in your bowel can also become more fragile after radiotherapy. This can cause blood to appear in your bowel motions. As other bowel problems are common in older men, it is also possible that symptoms are due to something else. So you may need to have a few tests to find out the cause of your symptoms. Tell your doctor or nurse if you have on-going problems with diarrhoea or bleeding from your back passage. 

For advice on eating, call our Cancer Nurseline on 1800 200 700 and ask for a free copy of the booklet Diet and Cancer. You can download the Diet and Cancer booklet here or get one from your local Daffodil Centre. Find your nearest Daffodil Centre here

Discomfort at your back passage

Radiotherapy to your prostate area may irritate your back passage and cause discomfort. It can also cause soreness around your anus.

You may notice some blood on toilet tissue after passing a bowel motion. If this happens, tell your doctor or nurse. Your doctor can prescribe medication that will help with this problem.

Skin changes 

During radiotherapy, the skin on your bottom or between your legs may become sore and a bit darker. It may even look like sunburn. It is best to avoid hot baths and to wear loose cotton clothes at this time.

When you wash the area, use warm water and pat it dry with a soft towel. Do not rub the skin while washing and drying. You can use a special cream to treat this problem but be sure to only use creams recommended by your nurse or radiation therapist. Avoid perfumed creams or powders. Check with your radiation therapist or nurse before applying anything to your skin.

Fatigue (tiredness)

Tiredness can build up over the course of your treatment. You may feel tired because of the treatment itself or perhaps you have to travel long distances for treatment. Rest as much as you need to and continue to do the things you like. But remember you may have less energy than before treatment. Regular gentle exercise such as walking can help to manage tiredness and increase your energy levels.

Depending on your job, you might continue to work during treatment or else take time off work. You may feel tired for some time but most men recover from their tiredness within a couple of months of finishing their treatment.

If you are having trouble with fatigue, a helpful booklet called Coping with Fatigue is available. You can download Coping with Fatigue here.Or call the Cancer Nurseline on Freephone 1800 200 700 and request a copy to be posted. Or visit your local Daffodil Centre if there is one in the hospital you attend. Find your nearest Daffodil Centre here


Radiotherapy for prostate cancer may cause infertility. If this happens, it means you cannot father a child in the future. If this is important to you, talk to your doctor about this effect before your treatment starts.

If you have a partner, it might help to see your doctor together so that you can both talk about your concerns. If your sperm count is normal, it may be possible to store your sperm before radiotherapy for later use. It is not safe to assume you are sterile after radiotherapy so will you still need to use contraception to prevent pregnancy.

Erectile dysfunction

Radiotherapy to your prostate can cause damage to the nerves and blood vessels that control erections. As the result, it can be difficult to get and keep an erection. This is called erectile dysfunction or impotence.

It can take up to 2 years for this side-effect to be noticed, but you might notice it sooner than that. Erectile dysfunction occurs in about 4 out of 10 men. If you have had problems with erectile dysfunction before radiotherapy, you are more likely to have problems with erections afterwards. Getting erectile problems will also depend on your age and general health. 

There is some evidence that taking tablets or using vacuum therapy for erectile dysfunction soon after radiotherapy may reduce your risk of erectile problems. At this time you may not be even interested in sex.

But taking the tablets or using a vacuum pump at an early stage may improve your chances of getting erections when you are ready to think about sex again.   You can discuss this with your doctor, nurse or GP. After radiotherapy, some men find that an orgasm has less semen than usual or they have a ‘dry’ orgasm, where no semen is ejaculated. 

For further information visit the section Sex, erectile dysfunction and prostate cancerPlease call our Cancer Nurseline on Freephone 1800 200 700 if you would like to talk to a cancer nurse in confidence. You can also email the nurses at cancernurseline@irishcancer.ie. You can also get publications and talk to a cancer nurse at your local Daffodil Centre. Find your nearest Daffodil Centre hereYou can also read further information about sex and prostate cancer here.

External beam radiotherapy - Small risk of another cancer

By receiving external beam radiation to the prostate gland there is a small chance of increasing the risk of developing another type of cancer in the future, although this is a rare occurrence. If this were to occur it would usually appear 5 to 10 years after radiation treatment has finished. It could occur in the bladder, colon or rectum - the areas near where the original radiotherapy was given.

Advantages and disadvantages of external beam radiation

The advantages and disadvantages of radiotherapy can be influenced by your age and general health as well as the stage of your prostate cancer. You can weigh up how this treatment relates to your situation and discuss it with your doctor or nurse.

Advantages of radiotherapy

  • It has none of the risks of a general anaesthetic and does not need overnight admission to hospital.

  • You may be able to work and carry on normal activities during the treatment.

  • You are not radioactive during or after the treatment so you can be in close contact to others.

  • Each treatment is relatively short. It usually takes about 15 minutes, although you may be in the radiotherapy department for up to an hour.

Disadvantages of radiotherapy

  • It may be difficult if you have far to travel to the radiotherapy unit as it involves treatment every week day for a number of weeks.

  • It may take some time to see how effective the radiotherapy has been.

  • You may become infertile.

  • There is a very low risk of getting a new second cancer in the longer term as a result of the treatment.

  • You might experience side-effects such as bowel or urinary problems, erectile dysfunction and fatigue. Some of these side-effects may get worse over the longer term.

  • You may not be able to have prostate surgery in the future due to the effects of the radiotherapy.

If you would like more information on radiotherapy, call our Cancer Nurseline on 1800 200 700 for a free copy of the booklet Understanding Radiotherapy or visit a Daffodil Centre. Find your nearest Daffodil Centre here. You might also like to view our webpage on radiotherapy for further information, watch a film about radiotherapy or read further information about radiotherapy here.

Date Last Reviewed: 
Monday, January 28, 2019