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Issues in Risk Assessment (1993) / Chapter Skim
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DEFINING AND DETERMINING THE MTD
Pages 80-90

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From page 80...
... Please use the print version of this publication as the authoritative version for attribution. suggested that the correlations result from the selection of data and the methods of analysis themselves and that they do not have a biologic basis.
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From page 81...
... Please use the print version of this publication as the authoritative version for attribution. agent during the chronic study that can be predicted not to alter the animals' longevity from effects other than carcinogenicity." The authors further stated that the dose should be one that "causes no more than a 10% weight decrement, as compared to the appropriate control groups, and does not produce mortality, clinical signs of toxicity, or pathologic lesions (other than those that may be related to a neoplastic response)
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From page 82...
... Please use the print version of this publication as the authoritative version for attribution. • The potential for one to obtain good dose-response data is present; without foreknowledge of the potency of the test substance, the potential is not often realized.
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From page 83...
... Please use the print version of this publication as the authoritative version for attribution.
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From page 84...
... On the general issue of TD50-MTD correlations, he says that "correlations between MTD and the TD50 occur as a result of the narrow range of possible potency values within a single experiment in relation to the wide variation observed in the potency of chemical carcinogens." He notes that fact in relation to "suggestions that the observed correlation between the MTD and the TD50 may simply be an artifact of the experiment designs currently used in carcinogen bioassay." He further stated that ''this does not imply that estimates of carcinogenic potency based on bioassay data are not meaningful, but does demonstrate that both the TD50 and q1* [the upper 95% confidence limit linear term in the linearized multistage dose-response curve]
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From page 85...
... Please use the print version of this publication as the authoritative version for attribution. range of carcinogenic potency, one should expect to find high correlations between separate species.
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From page 86...
... Please use the print version of this publication as the authoritative version for attribution. and potency, she found few materials that clearly resulted in low toxicity and high cancer potency.
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From page 87...
... Please use the print version of this publication as the authoritative version for attribution. (Moolgavkar and Venzon, 1979; Moolgavkar and Knudson, 1981)
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From page 88...
... Please use the print version of this publication as the authoritative version for attribution. place of cell proliferation in carcinogenesis said that "having looked at between 100 and 200 chemicals in animal bioassays [I find that]
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From page 89...
... Please use the print version of this publication as the authoritative version for attribution. a linear term in the fitted dose-response model.
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From page 90...
... Please use the print version of this publication as the authoritative version for attribution.APPENDIX A 90
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Key Terms

  • carcinogenic potency
  • low dose
  • lower doses
  • cell proliferation
  • low doses

  • highly carcinogenic
  • predict carcinogenic
  • toxic chemicals
  • bioassay data
  • current bioassays

  • cancer risk
  • produced cancers
  • dose extrapolation
  • define potency
  • produce tumors

  • low toxicity
  • dose risk
  • test substance
  • cell division
  • linearized multistage

  • using data
  • carcinogen bioassay
  • mtd induces
  • increase tumor
  • human equivalent

  • committee solicited
  • rodent carcinogenicity
  • gaylor discussed
  • earlier paper
  • chemically unrelated


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