Public health implications of carcinogenic exposure under the multistage model.

Mathematical implications of the multistage model of carcinogenesis are developed in order to answer important quantitative questions about environmentally induced cancer from the perspective of public health and intervention. Excess cancer incidence due to constant and interval exposure is examined theoretically for a stationary population under the multistage model of Armitage and Doll (Br J Cancer 1954;8:1-12). The time patterns for excess population incidence are simulated for the two types of exposure and the particular cellular change affected by the carcinogen. It is shown that the cumulative excess population incidence does not depend on which cellular change is induced by exposure and increases linearly with exposure duration. However, agents which affect earlier stages induce cancers which appear later in the population and, as a result, their detection by epidemiologic methods may be expected to occur later. Thus, such agents are more dangerous since control measures may be delayed, allowing greater cumulative incidence.