Cell kinetics, models, and cancer treatment--some principles for the radiation oncologist.

The radiation oncologist must attempt to apply the developments in the laboratory to the clinical situation in a manner that will result in a therapeutic gain. The possible influences of radiation fractionation and protraction, cell renewal and recruitment of normal or tumor tissues, differences in acute and late radiation effects and possible chemotherapy-radiation interactions are all factors that can affect the ultimate result. In order to develop a therapeutic gain, the effect on the tumor must be greater than on the normal tissues.