What is Radiotherapy and how does it work?

Radiotherapy uses high-energy rays to destroy cancer cells.  This treatment aims to treat cancer or relieve symptoms.

Radiotherapy uses carefully calculated doses of radiation to treat cancer as well as some non-malignant conditions.

It is painless and only takes a few minutes to deliver.

Radiotherapy can be used alone or with surgery, chemotherapy, or both.

It’s used to:

  • Attempt to cure cancer (radical radiotherapy)
  • Control/slow down the growth of cancer
  • Relieve cancer symptoms (palliative radiotherapy)

The type of radiotherapy you’re given will depend on the type of cancer you have and your individual situation:

  • External Beam – delivers radiation from outside the body using a Linear Accelerator (Linac)
  • Internal Radiotherapy – Brachytherapy delivers radiation to body cavities or tissues internally using a specialist machine. For more information see our page on Brachytherapy.


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.

Radiotherapy is often delivered in several small doses, over a specified period of days or weeks.  The prescription written by your Consultant Clinical Oncologist will define the dose and number of treatments (fractions).  Both short and long-term side-effects are possible and these are thoroughly discussed with you prior to starting treatment as part of the consent process.

For more information please visit Macmillan Information and Support.

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