Response of experimental animals to human carcinogens: an analysis based upon the IARC Monographs programme

Only the results of epidemiological studies can be used to establisha causal relationship between an exposure to an agent and humancancer; however, such studies often cannot be carried out dueto limitations of population or latent period or to the presenceof mixed exposures. It is essential, therefore, that the validitybe established of extrapolating to humans the results obtainedfrom long-term carcinogenicity tests in animals. The responsesof experimental animals to known and suspected human carcinogens,as evaluated in the IARC Monographs series, were analysed asan indication of the sensitivity of animal tests for predictinghuman carcinogens. Although the response was high - 84% - itwould have been even higher had all the compounds been adequatelytested experimentally. An additional finding was that for manyexposures causally related to human cancer, there is a targetorgan in common between humans and at least one animal species,despite many inherent physiological differences. These findingsshow clearly the importance of experimental carcinogenicitystudies in the primary prevention of cancer.