CALCULATING TUMOR-INCIDENCE RATES IN STOCHASTIC-MODELS OF CARCINOGENESIS

Multistage models of carcinogenesis are increasingly used in the estim ation of risks from exposure to environmental agents. The two-stage mo del of carcinogenesis is routinely used because it agrees with much of the existing tumor incidence data, parallels the biological two-stage model, and has much of its mathematical details derived. However, rec ent findings on the mechanisms of carcinogenesis has led researchers t o believe that there are a greater number of stages and a more complex structure to these models than a single pathway. In this paper, a met hod for readily computing tumor incidence rates for arbitrarily comple x multistage models is derived. The formulas for the two-stage model w ith time-varying rates are given explicitly. Simple rules for more com plicated models are given, and computer code able to implement these f ormulas are provided.