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What is radiotherapy?

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.

You can have radiotherapy either:

  • 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

About 4 out of 10 people with cancer (40%) have radiotherapy as part of their treatment.

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.

Last reviewed: 
10 Feb 2016
  • Radiotherapy: developing a world class service for England. 
    Report to Ministers from National Radiotherapy Advisory Group, 2007

  • De Vita, Hellman, and Rosenberg's Cancer: Principles and Practice of Oncology (9th edition)
    De Vita, V.T., Lawrence, T.S. and Rosenberg S.A.
    Lippincott, Williams and Wilkins, 2011

Information and help

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