ABSTRACT
Animals are given large doses to assure that a carcinogenic effect will be seen in the relatively small number that it is feasible to use in toxicology studies. Animal studies simply seem to be the simplest and most straightforward way to present concepts which form a basis from which to expand the discussion to other approaches. An emphasis in quantifying the time to tumor development would require different consideration in experimental design requiring more animals and more interim sacrifice of animals. A switch to a heterogeneous research animal population would introduce greater variability in the results, possibly necessitating more animals per dose level. Tumor incidence is ordinarily calculated as the number of tumor-bearing animals having tumors at a specific organ site divided by the total number of animals that survived long enough to have been at risk for that specific type of tumor.
