Implications of animal cancers to human neoplasia: Epidemiologic considerations

Wide variation in biologic and ecologic characteristics of the various animal species suggests opportunity for unique epidemiologic study of cancer; such studies may be designed to capitalize on species differences which permit the effective segregation and evaluation of factors suspected in the etiology of cancer in all species, including man. Epidemiologic exploitation of animal cancer models in the interests of the human problem is limited by the quality and quantity of disease occurrence and risk population data. The automated, nomenclature‐based Veterinary Medical Data Program of the National Cancer Institute (USPHS) has been adopted by a number of institutional veterinary college hospitals in the US and Europe, and serves as a source of detailed information on the occurrence of animal diseases seen at the participating facilities. Utilization of the case history relative‐odds study design promises to facilitate epidemiologic investigation of cancer in animals. Reported clusters of bovine lymphoma in dairy herds are unexplained and currently under study in an effort to evaluate possible genetic and viral factors. The analytic complications characteristic of human cancer cluster investigations are compounded in the case of animal cancer cluster studies. While a postulated relationship between the occurrence of cancer in man and animals is academically attractive, no such association has been demonstrated to date. Epidemiologic investigation of animal cancer models, while warranted and possible, must be designed so as to meet with limitations of available data.