English Abstract In this paper an attempt is made to develop a model for
radiation carcinogenesis essentially from first principles ; to demonstrate
that the model can describe both the age and dose dependent induction of
cancer in animals for widely differing exposure conditions ; and to outline
the implications of the model for radiation biology and protection. The
two-stage model for carcinogenesis developed by Knudson and Moolgavkar is
modified and combined with the molecular model for cellular radiation
effects to analyse radiation induced lung tumours in rodents for a variety
of radiation types and conditions. The combined model provides the
possibility of calculating the age dependent and dose dependent incidence of
cancer simultaneously. The model is used to fit data of lung tumours in
mice for acute exposures to X-rays, neutrons and to different dose-rates of
gamma-rays, and of lung tumours in rats exposed for longer periods to radon.
The satisfactory application of the combined model to animal data has led to
an examination of the implications of the model, which prove to be
far-reaching for the extrapolation of risk to low doses, the effect of life
time exposures and other aspects of radiation risk assessment. The combined
model predicts that the age dependent tumour incidence can follow either an
absolute risk type of pattern when exposure occurs at an older age, or a
relative risk type of pattern when exposure occurs at an early age. It also
predicts that the radiation effect is intimately related to the spontaneous
incidence and thus has implications for the transfer of risk across
populations.