Although ionising radiation can cause cancer, high doses can be directed at cancerous cells to kill them. This is called radiotherapy. About 40 per cent of people with cancer undergo radiotherapy as part of their treatment. It is administered in two main ways:

  • from outside the body using X-rays or the radiation from radioactive cobalt
  • from inside the body by putting radioactive materials into the tumour, or close to it

Some normal cells are also damaged by the radiation, but they can repair themselves better than the cancer cells are able to. Radiotherapy is often used together with chemotherapy – using chemicals which also kill cancerous cells.

A patient undergoing radiotherapy.
A patient undergoing radiotherapy