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General side effects of radiotherapy

Radiotherapy treatment for cancer can cause some general side effects, such as tiredness and sore skin. 

Why does radiotherapy cause side effects?

Radiotherapy aims radiation at cancer cells. But healthy cells nearby usually receive a radiation dose too. This then causes side effects.

Modern radiotherapy techniques are more precise and try to reduce the number and severity of side effects. 

Finding out about side effects

Before you start treatment your doctor should explain any possible side effects of the treatment. Knowing about the side effects can help you to prepare and manage any problems.

Ask about any possible long term side effects that the treatment may cause or anything you might be worried about. 

Side effects during treatment

Radiotherapy affects people in different ways, so it's difficult to predict exactly how you will react. Some people only have mild side effects but for others the side effects are more severe.

Some general side effects include:

Tiredness and weakness

You might feel tired or lack energy when you're having radiotherapy. This may last for a few weeks after the treatment ends. 

This can be because:

  • your body is repairing damage to healthy cells
  • you have low levels of red blood cells (anaemia)
  • you're travelling to the radiotherapy department each day

Some people do keep working during treatment. Whether you can or not depends on how you feel. Rest if you need to and try to exercise when you can. This can help to reduce tiredness. 

Sore skin

Some people get sore skin in the treatment area from radiotherapy. Your skin might: 

  • look red or darker
  • be dry and itchy
  • break and blister

The staff in the radiotherapy department can advise you on the best way of coping with this. They usually advise that you use a simple non fragranced moisturiser and to be gentle with the area. 

Loss of hair in the treatment area

Radiotherapy makes the hair fall out in the treatment area. It won't cause hair to fall out in other parts of your body. 

Your hair might grow back a few weeks after treatment ends. If it's unlikely to your doctor should tell you this before you start treatment.

Other side effects

Other side effects that you may have depend on the area of the body being treated. Tell your doctor, nurse or radiographer about any side effects.

They can help you find ways of reducing the effects and coping with them.

Possible long term side effects

For many people, the side effects of radiotherapy wear off within a few weeks of the treatment ending. But for some people radiotherapy can cause long term side effects.

The possibility of long term side effects depends on the type of cancer, its size and position. It might also depend on how close the cancer is to nerves or other important organs or tissues.

It is important to ask your doctor, specialist nurse or radiographer about the possibility of long term side effects. Depending on the position of the cancer the possible long term effects might include:

  • a change in skin colour in the treatment area
  • a dry mouth
  • breathing problems
  • loss of ability to become pregnant or father a child (infertility)
  • low sex drive
  • erection problems (impotence)
  • soreness and pain
  • bowel changes
  • bladder inflammation
Last reviewed: 
23 Jan 2019
  • External Beam Therapy (2nd edition) 
    Peter Hoskin
    OUP Oxford, 2012

  • Devita, Hellman and Rosenberg's Cancer Principles and Practice of Oncology (10th edition)
    VT Devita, TS Lawrence and SA Rosenberg
    Wolters Kluwer Health, 2015

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