Radiotherapy: technical aspects

Radiotherapy is involved in the treatment of at least 40% of cancer patients. Whereas palliative radiotherapy is typically given over 1–10 treatments, radical treatments can extend over 4–8 weeks. Radiation is delivered by external-beam machines or by inserting radioactive isotopes. Modern imaging, computing and delivery systems have led to dramatic improvements in external-beam radiotherapy. Treatment aims to accurately and precisely deliver high radiation doses to tumour tissue and minimize doses received by surrounding normal tissues. Image-guided radiotherapy increases accuracy by evaluating tumour motion during treatment. Stereotactic radiotherapy delivers very high radiation doses very accurately in a small number of treatments and is used for intra- and extracranial lesions. New developments aim to further improve treatment accuracy and precision, with the ultimate aim of increasing cure and reducing toxicity.