Cancer risks from ionizing radiation--a good arena to study the influence of age at exposure

1. Cancer risks from ionizing radiation--a good arena to study the influence of age at exposure • There is much epidemiological data relating age-specific and organ-specific cancer incidence to the magnitude of exposure and age at which it occurred • There is much animal data that is also age-specific, organ specific and for a variety of species and exposure patterns • There are a plethora of cancer risk models that can be applied to these situations • The time parameter in these models can be conveniently rescaled to relate to “biological processes” such as cell division • There are no complications from metabolic activation or inactivation processes

2. For n-stage models with (differential) growth, analytic solutions are available that allow for a variety of exposure patterns, building from piece-wise linear patterns or integrating over point patterns. The versions we use are described in two unpublished papers • “A Practical Approach to Using Epidemiological Data in Cancer Risk Assessment I: Risk Projections when there are Piece-wise Constant Exposure Histories” Robert L. Goble and Chao Chen, June 1997 • “Insights from the Multistage Model into the Age-Dependence of Carcinogenic Effects” Weihsueh Chiu, December 2002

3. Here are some results from a very simple model: 5-Stages, no growth, and alternative effects of early life exposure on mutations at various stages