A Comparison of Regulatory Implications of Traditional and Exact Two-Stage DoseResponse Models Academic Article uri icon


  • We compare the regulatory implications of applying the traditional (linearized) and exact two-stage dose-response models to animal carcinogenic data. We analyze dose-response data from six studies, representing five different substances, and we determine the 'goodness-of-fit' of each model as well as the 95% confidence lower limit of the dose corresponding to a target excess risk of 10-5 (the target risk dose TRD). For the two concave datasets, we find that the exact model gives a substantially better fit to the data than the traditional model, and that the exact model gives a TRD that is an order of magnitude lower than that given by the traditional model. In the other cases, the exact model gives a fit equivalent to or better than the traditional model. We also show that although the exact two-stage model may exhibit dose-response concavity at moderate dose levels, it is always linear or sublinear, and never supralinear, in the low-dose limit. Because regulatory concern is almost always confined to the low-dose region extrapolation, supralinear behavior seems not to be of regulatory concern in the exact two-stage model. Finally, we find that when performing this low- dose extrapolation in cases of dose-response concavity, extrapolating the model fit leads to a more conservative TRD than taking a linear extrapolation from 10% excess risk. We conclude with a set of recommendations.

published proceedings

  • Risk Analysis

author list (cited authors)

  • Chiu, W. A., Hassenzahl, D. M., & Kammen, D. M.

citation count

  • 0

complete list of authors

  • Chiu, Weihsueh A||Hassenzahl, David M||Kammen, Daniel M

publication date

  • February 1999