Radiotherapy is the use of radiation in controlled doses to treat cancers. lt works by damaging the DNA of malignant cells. Radiotherapy may be used:

* as curative treatment, for example to shrink tumours

* as adjuvant treatment, alongside or following chemotherapy -treatment with anti-cancer drugs

* in lower doses as palliative treatment to reduce pain and other symptoms of cancer or disease, but not as a cure.

A radiologist determines the dose and the exact target for the radiation beams. Dosage is measured in grays (Gy). A daily dose is a fraction. Radiotherapy can also be delivered internally by radioactive implants such as needles, or by liquids such as strontium for some bone cancers.

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