ABSTRACT
Key points 189 Bibliography 189 Further reading 190
Despite optimum conformation of the treatment fields to the tumour and precise treatment planning and application, the target volume in curative radiotherapy necessarily includes a substantial amount of normal tissue, for several reasons. First, malignant tumours infiltrate microscopically into normal structures, which hence must be included into the high-dose volume as a tumour margin. Second, normal tissues within the tumour, such as soft tissue and blood vessels, are exposed to the full tumour dose. Third, normal structures in the entrance and exit channels of the radiation beam may be exposed to clinically relevant doses. Therefore, effective curative radiotherapy is unavoidably associated with an accepted risk for early and late radiation side-effects (‘adverse events’) in order to achieve adequate tumour cure rates.
