Figure 3.

Comparisons of observation INC(h,t) (black circles) to CAL(h,t) (red, blue crosses) for the two-stage cancer model amended for limiting tumor initiation mutations to the fetal/juvenile stem cells and n = 2, m = 1. A remarkably good fit is obtained for the assumptions that the population is homogeneous for risk factors such as oncomutation rates and/or preneoplastic growth rates (F = 1) and there are no competing synchronous forms of death (f = 1) [red crosses, GOF(h,t) = 0.085]. However, a significantly lower value, GOF(h,t) = 0.043 is observed when population risk stratification is assumed (F < 1). Allowing for the possibility of an unknown competing synchronous form of death (f < 1) did not decrease the values of GOF(h,t) further. These findings are spurring further amendment of the two-stage model to use stratified variables for initiation and promotion mutation rates, preneoplastic growth rate and number of stem cells at maturity.