ABSTRACT
At many meetings someone or other expresses the view that the ideal animal for use for the carcinogenicity testing of a compound is the one that metabolizes it in the same way as man. For a carcinogenicity test to be meaningful, it must be conducted in a sufficiently large number of animals to permit a statistically significant effect on cancer risk to be seen. It could be more expensive to identify a species that mimics man than to carry out a carcinogenicity test in a rodent. The high incidences of testicular, pituitary and mammary tumours in many strains of rats and the high incidences of liver, lung and lympho-reticular neoplasms in many strains of mice are serious handicaps to meaningful predictive carcinogenicity testing. In rats, overfeeding predisposes to all manner of endocrine disturbances and these are bound to distort the response of animals exposed to chemicals in carcinogenicity tests.
