Radiotherapy: targeting tumours and evaluating risk

Use ionisation to damage cancer cells

Radiotherapy uses ionising radiation to destroy cancer cells or stop them reproducing. In external treatment, a beam such as gamma radiation is aimed at a tumour from outside the body. Radiation deposits energy in tissue and damages cells. Healthy cells can also be harmed, so the treatment must be planned to give the tumour an effective dose while limiting unnecessary exposure of surrounding tissues.