Kinetics Model for Initiation and Promotion for Describing Tumor Prevalence From HZE Radiation

A kinetics model for cellular repair and misrepair for describing multiple radiation-induced lesions (mutation-inactivation) is coupled to a twomutation model of initiation and promotion in tissue to provide a parametric description of tumor prevalence in the Harderian gland in a mouse. Doseresponse curves are described for -rays and relativistic ions. The e ects of nuclear fragmentation are also considered for high-energy proton and alphaparticle exposures. The model described provides a parametric description of age-dependent cancer induction for a wide range of radiation elds. We also consider the two hypotheses that radiation acts either solely as an initiator or as both initiator and promoter and make model calculations for fractionation exposures from -rays and relativistic Fe ions. For fractionated Fe exposures, an inverse dose-rate e ect is provided by a promotion hypothesis using a mutation rate for promotion typical of single-gene mutations.