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

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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

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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in two unpublished papers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

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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
Model Mutation rate per .1 life Stage affected Lifetime absolute cancers Age at flash exposure (life)
I--only stage 1 affected .00674 1 20 6.2 (age 5 in an 80 yr life)
II--only stage 4 affected .00674 4 10.01 6.2
III--Pierce Mendelson .0013 for each stage all 12.6 6.2
IV--smoking /radon analog .0045/ .00225 1 4 16.9 6.2
Back ground .000023 all 10 lifetime
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