Radiotherapy (radiation therapy) uses high energy rays, usually x-rays, to kill cancer cells. It is a localised treatment. This means it kills cells only in the area of the body which it is pointed at and nowhere else. Cancer cells are more sensitive to radiotherapy than normal cells and more will be killed. Normal cells which are affected usually recover or repair themselves quite quickly. Any side effects which occur during treatment are usually temporary. There may be a small risk of long term or late, permanent effects from radiotherapy.