Biologically based treatment planning.

The classical way of quantifying dose-response relations for tumors and normal tissues and their dependence on the genetic make up of the patient is briefly reviewed. Response quantifiers such as quality of life and the probability of achieving a complication-free cure are helpful in solving many of the problems of radiation therapy planning. It is shown, through the use of these quantifiers, that by introducing radiobiologically optimized, intensity-modulated dose delivery, the treatment outcome can be improved by as much as 20%, and more in cases with a complex spread of the disease. The real strength of the radiobiological models is to serve as a scientific tool for the development of treatment optimization so that the models are modified when the clinical response systematically deviates from the predictions of the models. In this way, the biological models serve as a continuously updated historical database that later on may replace the control arm in clinical trials and allow all patients to benefit from the latest developments in radiobiologically optimized treatment techniques.