Statistical analysis of disease onset and lifetime data from tumorigenicity experiments.

We present and discuss several methods for analyzing rodent tumorigenicity experiments. Two approaches are based on the age and tumor status (present/absent) of each animal at the time of death, and assume either that the tumor type is nonlethal or instantly lethal. Two other approaches avoid such restrictive assumptions about tumor lethality by requiring additional types of data. One method assumes that animals are randomly sacrificed at various ages throughout the study. The second approach requires that each animal which develops the tumor be classified as dying either from the tumor or from other causes.