Age-specific models of mortality and tumor onset for historical control animals in the National Toxicology Program's carcinogenicity experiments.

This paper models general survival and the distribution of tumor onset times for various tumors in the data base of control animals developed by the National Toxicology Program. For general survival, a modified Weibull model is shown to give an adequate fit for both Fischer 344 rats and C57BL/6 X C3H F1, mice. In addition, data from control animals in a lifetime study of asbestos are used to support the extension of these survival curves beyond 2 years in Fischer rats. The distributions of tumor onset times are modeled using a two-parameter Weibull model. For many common tumor types, this model yielded a very good fit to the data. Finally, a summary measure of the contribution of a tumor to mortality is given.