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Side effects of radiotherapy for anal cancer

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This page tells you about the side effects of radiotherapy for anal cancer.


A quick guide to what's on this page

Radiotherapy for anal cancer – side effects

Side effects of radiotherapy usually start during the course of treatment and carry on for a week or two after treatment has finished. Side effects can include

  • Tiredness
  • Sore skin around the anus and groin
  • Bladder irritation
  • Opening your bowels frequently
  • Feeling sick

Your doctor will prescribe painkillers to help with skin soreness. He or she can also give you medicines to stop you feeling sick or to control diarrhoea. Your nurse will advise you on how to care for sore or broken skin.

Drinking plenty of water is important if your bladder is irritated, or if you have diarrhoea or are feeling sick. Wearing loose clothes and underwear will help with sore skin. You might also need a soft cushion to sit on.

Long term side effects

Some people get long term side effects from radiotherapy. These can start a few months or even a couple of years after treatment. They include frequent bowel movements and passing urine more often. Women may have dryness or shrinkage of the vagina and an early menopause. Men may have difficulty getting an erection.


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Short term side effects

Short term side effects for radiotherapy usually start during the course of treatment and carry on for a week or two after treatment has finished. These side effects can include

Feeling tired

You may find that you become more and more tired as your treatment goes on. This is very common with radiotherapy. It is partly the travelling to and from hospital, and partly an effect of the treatment itself.

Don’t be afraid to rest if you need to. It is good to try to get some exercise each day, however gentle. But if you feel like you want to have a lie down, then you probably need to do just that. There is more information about coping with tiredness in the cancer fatigue section.

Sore skin around the anus and groin

Radiotherapy can make the skin around the anus, genitals and groin sore. Radiographers use newer machines nowadays which means that this happens less often than it used to. But the skin in this area, particularly around the anus, is very sensitive and will get quite red and sore during your radiotherapy treatment. It may break down. This can make opening your bowels very painful. Your doctor will prescribe painkillers to help until your skin heals up. And you may need a soft cushion to sit on for a while. Wearing loose, comfortable underwear and clothing also helps during this time.

Your nurse will advise on how to care for your skin. Keeping the area clean is important but washing can make the soreness worse. You should only wash the area with plain water and simple soaps such as baby soap. Gently pat the skin dry with a soft towel. Or use a hairdryer on a cool setting. Don’t use perfumed or medicated soaps or other products unless you have discussed them with your specialist, radiotherapy nurse or radiographer.

Bladder irritation

The bladder is very near the bowel and rectum, so radiotherapy to the bowel often irritates the bladder. You may feel

  • As if you have cystitis (a bladder infection)
  • As though you want to pass urine all the time, but when you go there isn’t much there
  • A burning pain when you do pass urine

Try to drink plenty of fluids. Many people find drinking cranberry juice can be particularly helpful with bladder problems (although if you are taking an anti clotting tablet called warfarin you should check with your blood clinic first). Your bladder irritation will settle down after the treatment is over, but let your doctor know if it continues, in case you have an infection that needs treating with antibiotics.

Opening your bowels frequently

This is quite common after radiotherapy to the anus. It happens because the radiotherapy causes irritation and inflammation of the anus and rectum. This means your rectum can’t hold your stools (faeces) as well as normal. You will also have sore skin around the anus, which can make opening your bowels painful. Tell your doctor and nurse about any pain you have so they can make sure you have the most appropriate painkillers. Your doctor might also prescribe drugs to help reduce the irritation and inflammation, which may help you not to open your bowels as often. These include steroid enemas if the problem is severe. The irritation and inflammation usually settles down about 2 to 3 weeks after your radiotherapy treatment ends.

You may get diarrhoea, particularly if you are also having chemotherapy. You may need drugs to control diarrhoea. Drinking plenty of fluids and having a low fibre diet may also help. The radiographer or radiotherapy nurse can tell you about this, and may have leaflets about diet. A low fibre diet means not eating all the high fibre foods we are always told are so good for us! A low fibre diet includes

  • Cutting out whole grain cereals and wholemeal bread
  • Not eating too many helpings of fibrous vegetables, fruit or fruit juice

Feeling sick

Your doctor can give you medicines to stop you feeling sick, so it is important to tell your doctor or nurse if you feel sick.

You may not feel like eating or drinking much if you are feeling sick. But it is important to drink plenty of fluids if you can. If you are having trouble eating, try having high calorie drinks. You can get these on prescription, or buy them from your chemist. There is more information about managing sickness and diet problems in the section on coping physically with cancer.


Long term side effects of radiotherapy

As well as short term side effects while you are having treatment, radiotherapy can cause long term side effects in some people. Your doctor will make every effort to make sure you have as few side effects as possible. But some people are more sensitive than others to radiation. At the moment, doctors can’t tell who is and who isn’t sensitive before they give them radiotherapy.

Long term side effects are more likely with higher doses of radiation. So if you are having a short course of radiotherapy to help with symptoms, you are unlikely to have long term effects.

The long term effects can begin from a few months to a couple of years after you finish your course of treatment. The long term side effects of radiotherapy to the bowel or rectum may include

  • Frequent bowel movements
  • Passing urine more often, as your bladder can become hardened (fibrosed) and shrink a bit
  • Difficulty in passing urine, as the tube from the bladder to outside your body (urethra) may become more narrow
  • Extra blood vessels can grow in your bladder and rectum, which may cause blood in your urine and stools
  • Dryness and shrinkage of your vagina, making sex uncomfortable. This may be kept to a minimum by using vaginal dilators after treatment has finished
  • Difficulty getting an erection
  • Loss of fertility for men and women
  • Early menopause
  • Weak muscles in the anus, leading to incontinence
  • Chronic diarrhoea and weight loss
  • Damage to the bones of your hip

Talk to your doctor if you think you have developed any of these side effects. It may be that your symptoms are due to something else (for example, a bowel or bladder infection). If you do have a side effect, your doctor may be able to help manage your symptoms.

Some of the side effects affecting your bladder or bowel may be helped by regular pelvic floor exercises. Your nurse, physiotherapist or continence advisor can give you information about this.

If you smoke, it is a good idea to stop before you start radiotherapy treatment. It may help to reduce the side effects caused by treatment, as well as improving your general health.

Stopping smoking can be difficult, particularly when you are going through a stressful time. Do talk to your doctor or nurse about support for stopping smoking


Where to find more about radiotherapy side effects

Look at the radiotherapy section for more information about radiotherapy and side effects. There is a section called radiotherapy - stomach and abdominal side effects, which you may find helpful.

There is also information for women about coping with an early menopause and vaginal dryness. And in the sex and anal cancer section, there is information for men about difficulty getting an erection.

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Updated: 12 February 2014