Radiotherapy is the use of radiation in medicine as part of treatment (as opposed to radiology, which is the use of radiation in medical imaging and diagnosis).
Radiotherapy is commonly used for the treatment of tumours, usually as an adjunct to surgery and/or chemotherapy. The most common tumours treated with radiotherapy are gynaecological tumours, prostate cancer, bladder cancer and rectal cancer.
Occasionally radiotherapy is used as part of palliative treatment, where cure is not possible and the aim is for symptomatic relief.
Two main divisions of radiotherapy are external radiotherapy and internal radiotherapy, the difference being that in external radiotherapy, the radiation source is from outside the body whereas in internal radiotherapy radioactive material is implanted within the body.