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General side effects of radiotherapy

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 will 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 else you might be worried about. 

Side effects during treatment

Radiotherapy affects people in different ways, so it's difficult to predict exactly what side effects you will have and how bad they might be. Some people only have mild side effects but for others the side effects can be 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
  • become more sensitive
  • 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 continue to use your normal moisturiser unless this begins to irritate your skin. Or use a simple non fragranced moisturiser and to be gentle with the area.

Continue to protect the treated area from the sun for at least one year after you have finished treatment. Your skin will be more sensitive, so use sunscreen with SPF 50 (sun protection factor 50). 

Ask your radiographer if you have any concerns.

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
  • red spidery marks on your skin (telangiectasia) caused by broken blood vessels
  • 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
  • drainage channels to the arms or legs can become partly blocked resulting in swelling called lymphoedema

Information and help