Issues in Risk Assessment (1993) / Chapter Skim
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USE OF THE MAXIMUM TOLERATED DOSE IN ANIMAL BIOASSAYS FOR CARCINOGENICITY
USE OF THE MAXIMUM TOLERATED DOSE IN ANIMAL BIOASSAYS FOR CARCINOGENICITY
Pages 3-8
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From page 3... ...
The committee chose as its first task to address the use and limitations of MTD testing in long-term animal bioassays for carcinogenicity. The first report focuses specifically on whether the MTD should continue to be used in carcinogenicity bioassays, and it does not address all the issues related to performing carcinogenicity bioassay or interpreting their results.
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Please use the print version of this publication as the authoritative version for attribution. The committee concluded that the correlations are not wholly mathematical or statistical artifacts, but are due partially to an underlying relationship between measures of general toxicity (e.g., the MTD)
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But tests conducted at lower doses will probably have little power to detect carcinogenic effects, unless the number of animals tested is increased immensely, which would increase the cost of a bioassay commensurately; the large number of animals required for detection of the smaller increase in tumors incidence that might occur at low doses is one of the primary reasons for use of the MTD in carcinogenicity bioassays. Testing at doses that induce overt toxicity, however, can lead to changes in an animal's food consumption, recurrent cytotoxicity, and hormonal imbalance, all of which an increase or decrease carcinogenic responses at particular target sites.
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redefine the MTD, basing it on studies of the dose dependence of physiologic effects expected to alter carcinogenic response; and (4) use MTD testing as part of an overall testing strategy that separates carcinogens from noncarcinogens but also provides additional information useful for determining human relevance.
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The minority recognizes that chronic animal bioassays were originally designed to answer a simple question: Can chemicals cause cancer in animals? It is clear that the primary motivation for conducting the chronic bioassay today, however, is to determine whether the substances tested are likely to pose a substantial cancer risk to human populations.
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Please use the print version of this publication as the authoritative version for attribution. mors develop.
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