Analysis of neoplasia in life-span radiation effects studies in animals

Analysis of the occurrence of neoplastic disease in animals on life-span radiation effects experiments presents some unique problems. A simple analysis of tumor incidence or prevalence may overlook differences in the nature of specific types of neoplasms which can be extremely important in interpreting the results. Analyses should address not only whether or not an animal has a particular tumor type, but should also address the ultimate effect of that tumor on the fate of the animal. For life-span studies in dogs, where multiple neoplasms in individual animals are the rule rather than the exception this is particularly important. An easily computerized approach to performing such analyses has been adapted from a previous work. Neoplasms are classified as incidental (those found at necropsy in dogs which died of an unrelated cause), mortality-independent (those seen in live dogs and diagnosed after surgical removal), or fatal (those directly or indirectly responsible for death). In the authors' studies such categorization has allowed the evaluation of the overall impact of a tumor on an animal and enhanced the understanding of the meaning of experimental results. Adoption of a similar approach by various groups performing radiation effects studies in animals would facilitate the comparative evaluation of data from these studies