ABSTRACT
Therapeutic ratio When considering how to achieve the best outcome from radiotherapy in the treatment of tumours, it is critical to understand the concept of therapeutic ratio. Cure is always achieved at some cost in terms of normal tissue damage. There must be a balance between trying to ensure that all tumour cells receive a lethal dose of radiation and that acute and late effects are tolerable. The total dose, dose per fraction, treated volume and addition of drugs (radiochemotherapy) will all affect this balance, as will individual factors for each patient (e.g. age, comorbidity and intrinsic tissue radiosensitivity).
