Radiotherapy is the treatment of disease by means of ionising radiation. It may be used in treatment of malignant disease, either to attempt to curatively ablate a tumour, to reduce its size prior to operative removal or to paliate symptoms. It is often used for the treatment of malignant bone pain.
In the past it has been used for inflammatory diseases such as ankylosing spondylitis, but due to the increased occurence of secondary tumours this practise no longer occurs.
The affected tissue may be exposed to a beam of radiation, or a radioactive element may be contained in devices and introduced directly into the tissue or it may be introduced into a natural body cavity.
The success of radiotherapy is based on the therapeutic ratio, where it is possible to administer a dose of ionising radiation to an area such that normal tissues recover from the damage and neoplastic tissues do not.