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Radiotherapy uses radiation:

  • to cure cancer by killing cancer cells
  • to control symptoms, such as relieving pain as part of palliative care
  • before surgery, to make a tumour smaller so it is easier to remove
  • after surgery, to destroy any parts of a tumour that may be left

You usually have it as a course of treatment over a number of days or weeks, coming into hospital to have the radiotherapy and going home again the same day. You may have it as part of a combination of treatments, such as chemotherapy and surgery.

It is painless and you are not radioactive after having the treatment. You can go home on public transport and do not need to avoid other people.

Before the treatment you may have ‘radiotherapy planning’. This is to locate and mark which area needs to be treated. First you have a CT scan. Then, using the images from the scan, some very small permanent marks are placed on your skin so the doctors can be sure they treat exactly the same area every day.

You usually have radiotherapy at either Guy’s or St Thomas’ Hospital.

Types of radiotherapy

You can be given radiotherapy in various ways:

  • Externally: this uses radiation such as high-energy x-ray beams that are aimed at the tumour from a machine and destroy the cancer cells in the treatment area.
  • Internally: you drink a radioactive liquid that is taken up by cancer cells or you have radioactive material put in or close to the cancer. This includes SIRT (selective internal radiation therapy) and radioactive iodine therapy.
  • Radiosurgery: this is a specialist type of external radiotherapy used to treat certain tumours. You have no actual surgery. Large, precise doses of radiation are focused on the tumour for a short time. Examples includes gamma knife and cyberknife radiosurgery.

Radiotherapy can cause side effects. These are often mild and easily treated. Severe side effects are very rare. We will ensure you get all the support you need to cope with the effects of your treatment.

Go to for more information about radiotherapy.