[General principles of dose-effect relationship]

The principles of chemotherapy administration are based on its haematological toxicity. In 1979, Goldie and Coldman described a mathematical model to demonstrate the link between the dose schedule and the cytotoxicity. Some years later, Norton and Simon developed this concept by integrating a tumour growth model taking into account the parameters of the in vivo tumoral homeostasis. The limits of the results obtained in the treatment of many cancers and the recent development of haematopoietic supports has led the clinicians to reconsider the therapeutic modalities and to intensify the treatments. We recall herein the principles of therapeutic intensification. In introduction of the various clinical applications, this chapter briefly calls back the theoretical bases of the concepts of dose response, dose-density and dose-intensity.