A measure of tumorigenic potency incorporating dose-response shape

Many researchers have considered the problem of ranking chemical agents based on their carcinogenic potency. Sawyer et al. (1984, Biometrics 40, 27-40) proposed a carcinogenic potency estimate that incorporates both intercurrent mortality and background tumor rates. Since then, many authors have either generalized the method outlined by Sawyer et al. or developed their own method based on a slightly different adjustment for treatment-related changes in survival. None of these methods, however, has estimated the shape of the dose-response curve and incorporated such an estimate in potency estimation. In this manuscript, a measure of tumorigenic potency is proposed that utilizes the estimated shape of the dose-response relationship, in addition to estimated dose effects, in order to rank chemicals on the basis of carcinogenic risk. Comparison of this new measure to that of Sawyer et al. is done using a large database of animal carcinogenicity experiments from the National Cancer Institute and the National Toxicology Program.