General side effects of radiotherapy | Cancer Research UK
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Why radiotherapy causes side effects

Radiotherapy destroys cancer cells in the area of the body it is aimed at. The treatment also affects some of the normal cells nearby. Radiotherapy affects people in different ways, so it's difficult to predict exactly how you will react. Some people have only mild side effects but for others the side effects are more severe.


Finding out about side effects

Before you start your treatment, talk about any likely side effects with the staff in your radiotherapy team. Knowing about the side effects can help you to prepare and to manage any problems.

Ask about any possible long term side effects that the treatment may cause.


Side effects during treatment

The main side effects of radiotherapy treatment include 

  • Tiredness and weakness
  • Sore skin
  • Loss of hair in the treatment area

Tiredness and weakness

Most people feel tired while they are having radiotherapy, particularly if they are having treatment over several weeks. This is because the body is repairing the damage to healthy cells. Or tiredness can be due to low levels of red blood cells (anaemia). 

You might also feel weak and as though you don't have the energy to do your normal daily activities. This may last for a few weeks after the treatment ends. Rest if you need to and try to exercise a little when you can. This can help to reduce the tiredness.


Sore skin

Some people get sore skin in the area being treated. The skin may look reddened or darker than usual. It may also get dry and itchy. The skin may break or small blisters can start to form in the area. The staff in the radiotherapy department can advise you on the best way of coping with this.


Loss of hair in the treatment area

Radiotherapy makes the hair fall out in the treatment area. Hair in other parts of the body is not affected. The hair should begin to grow back again a few weeks after the treatment ends.


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. They can give you leaflets which describe the side effects.


Possible long term side effects

For many people the side effects of radiotherapy wear off within a few weeks of the treatment ending, and they can go back to a normal life. But for some people radiotherapy can cause long term side effects. The possibility of long term side effects depends on the type of cancer and 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 may 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)
  • Long term soreness and pain
  • Bowel changes
  • Bladder inflammation

More information about radiotherapy

Find out about

The radiotherapy team


Coping with tiredness

Preventing and dealing with skin soreness

Coping with hair loss

For side effects in a specific area look at your type of cancer

For general information and support

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

Share experiences on our online forum – Cancer Chat

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Updated: 14 March 2016