About radiotherapy side effects

Radiotherapy uses radiation to treat cancer. It aims to give a high dose of radiation to the cancer but as low a dose as possible to the surrounding healthy cells. This gives the highest chance of curing or shrinking the cancer, while reducing the risk of side effects.

While radiation kills the cancer cells, the normal cells are usually able to recover. And your side effects generally get better over a few weeks.

Finding out about side effects

Before you start treatment your doctor will explain any possible side effects of the treatment. They will also discuss the best way to manage them. Knowing about the side effects can help you to prepare for them. Usually the side effects improve a few weeks after treatment. But some might continue long term.

Ask your doctor 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. 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 radiotherapy side effects include:

  • effects on your blood
  • problems eating and drinking
  • tiredness
  • skin reactions
  • effects on your sex life and fertility
  • emotional effects

You have different side effects depending on which area of the body is being treated. Tell your radiotherapy team about any side effects you have.

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 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

Worries about treatment side effects

You may feel anxious about radiotherapy side effects and this is normal. It can help to talk through any worries you have with your doctor, nurse or radiographer.

  • External Beam Therapy (Radiotherapy in Practice) Third Edition
    Peter Hoskin
    Oxford University Press, 2019

  • Devita, Hellman and Rosenberg's Cancer: Principles and Practice of Oncology (12th edition)
    VT Devita, TS Lawrence and SA Rosenberg
    Wolters Kluwer Health, 2023

  • Walter and Miller's Textbook of Radiotherapy: Radiation Physics, Therapy and Oncology (8th edition)
    R Symonds, J A Mills and A Duxbury
    Elsevier, 2019

Last reviewed: 
26 Feb 2024
Next review due: 
26 Feb 2027

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