Long term side effects of radiotherapy | Cancer Research UK
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Long term side effects of radiotherapy

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Find out about the possible long term side effects of radiotherapy. You can find information about


General long term effects 

All cancer treatments can have long term side effects. Depending on the area of the body you have treated, you may have any of these changes after radiotherapy

  • Your skin might look darker in the treated area – as if it is suntanned
  • Your skin may feel different to touch
  • Your hair might grow back a different colour or texture in the treatment area
  • You may have permanent hair loss within the treated area
  • You may develop red spidery marks on your skin (telangiectasia) caused by small broken blood vessels
  • Drainage channels to the arms or legs can become partly blocked resulting in swelling called lymphoedema
  • You might be unable to become pregnant or father a child if your ovaries or testicles were in the radiotherapy field

Long term effects on tissue

Radiotherapy makes tissues less stretchy. Doctors call this radiation fibrosis. How this affects you will vary depending on which part of your body was treated. Fibrosis may cause any of the following.

  • Your bladder could become less stretchy and hold less urine if you have abdominal treatment, so you need to pass urine more often
  • Your breast might feel firmer (harder) after breast radiotherapy
  • Your vagina could become narrower and less stretchy after pelvic treatment
  • Your arm may swell if your shoulder was treated
  • Your leg may swell if your groin was treated
  • Breathlessness due to your lungs being less stretchy after treatment to the lungs or chest
  • Narrowing of the food pipe (oesophagus) making it difficult to swallow, after treatment to your neck or chest

Long term effects on the pelvis

Radiotherapy to the pelvic area may cause

  • Bowel changes and diarrhoea – medicines can help to reduce this
  • Bladder inflammation causing pain and a feeling of needing to pass urine
  • Abdominal pain due to urine infection, bowel changes or fine cracks in the pelvic bones

These changes can gradually appear over a long time, sometimes several years. If you had radiotherapy in the past and are worried about side effects, ask to go back to your radiotherapy department and talk to the doctor.


Preventing side effects

Modern radiotherapy treatments are designed to give as few permanent side effects as possible. The machines that plan and give the radiotherapy today are more sophisticated and accurate than they have ever been. 

Doctors have to balance the chance of cure with the risk of side effects. The higher the dose of radiation, the more likely you are to have side effects. But if you don't have a high enough dose, the chances of controlling or curing your cancer are lowered. So, you can't avoid the risk of side effects completely.

Doctors have learned more about what causes side effects. They try to prevent them happening as far as they possibly can. One of the ways doctors try to prevent long term side effects is to make sure that only a safe amount of treatment is given to any part of the body.

Each part of the body has a radiotherapy limit and this varies depending on how sensitive that part of the body is to radiation. Doctors know from experience what that limit is. But they have no reliable way of knowing how each person will react to treatment. Some people seem to be more sensitive to radiation than others. So far, we can't pick out before treatment who is likely to be sensitive.

If treatment needs to be given from different angles, doctors make sure that the radiotherapy fields don't overlap too much. This helps to stop side effects because areas that overlap are exposed to more radiation.


Newer ways of giving radiotherapy

Doctors have changed and developed the way they give radiotherapy. They make sure that the highest radiotherapy dose is concentrated on the cancer as much as possible. They are trying to improve cancer treatment all the time. 

Current radiotherapy techniques shape the radiotherapy beams to fit the cancer very precisely. This is called conformal radiotherapy. Conformal radiotherapy means that less normal tissue is in the radiotherapy treatment area to reduce the risk of side effects.

A highly conformal type of radiotherapy is intensity modulated radiotherapy. Some radiotherapy machines take scans around the time that the treatment is given and this is called image guided radiotherapy.

It is important to remember that radiotherapy only affects the part of the body that is treated. If there are any changes to a part of the body outside the treatment area, these won't have been caused by your treatment.


More information about radiotherapy

Find out about

Internal radiotherapy

External radiotherapy

Side effects of radiotherapy

Lymphoedema (swelling)

Shortness of breath

Books and resources about radiotherapy treatment

For general information and support

Contact the Cancer Research UK nurses on freephone 0808 800 4040 (Open 9am to 5pm, Monday to Friday)

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Updated: 24 March 2016