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What radiotherapy is

Nurse and patients talking about cancer

This page tells you about radiotherapy treatment. There is information about



Radiotherapy means the use of radiation, usually X-rays, to treat illness. X-rays were discovered in 1895 and since then radiation has been used in medicine for diagnosis and investigation (X-rays) and treatment (radiotherapy).

Doctors have a lot of experience with using radiotherapy in medicine. About 4 out of 10 people with cancer (40%) have radiotherapy as part of their treatment. It is given in various ways, including

  • From outside the body as external radiotherapy, using X-rays from linear accelerator machines, electrons, and more rarely other particles such as protons
  • From within the body as internal radiotherapy, by drinking a liquid that is taken up by cancer cells or by putting radioactive material in, or close to, the tumour

How radiotherapy works

Radiotherapy destroys the cancer cells in the treated area by damaging the DNA within these cells. Although normal cells are also affected by radiation, they are better at repairing themselves than the cancer cells.


Aim of radiotherapy treatment

The radiotherapy team plans each person's radiotherapy individually. The treatment aims to give a high dose to the cancer but as low a dose as possible to the surrounding healthy cells. The healthy cells can then recover. 

This aims to give the highest chance of curing or shrinking the cancer while reducing the risk of side effects.


Worries about treatment

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


More information about radiotherapy

We have detailed information about

You can phone the Cancer Research UK nurses on freephone 0808 800 4040. The lines are open from 9am to 5pm, Monday to Friday. They will be happy to answer any questions that you have.

Our general organisations page gives details of people who can provide information about radiotherapy. Some organisations can put you in touch with a cancer support group. Our cancer and treatments reading list has information about books, leaflets and other resources about radiotherapy treatment.

If you want to find people to share experiences with online, you could use Cancer Chat, our online forum.

120,000 benefit from radiotherapy each year

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Updated: 10 February 2016