[Life span and tumor incidence in animals of various species]

The data presented shown no positive correlation between spontaneous tumour incidence and (1) the life span of species, (2) the life span of different strains or stocks of the same species, and (3) the life span of certain populations of the same strain or stock. This conclusion is in conflict with the concept suggesting a summation effect of the events that cause malignant development irrespective of aging per se, in the age-related increase in the tumour incidence, and indicates an important role of age-related changes occurring in the organism in the realization of carcinogenic effect of endogenous and/or exogenous factors.