>"pediatric malignancies"
maybe, or you can use the full Armitage and Doll model I described above and replace t with something like a discrete exponential decay where N(t) = number of divisions since zygote as a function of time. Ie N(t) = N0(1 - k)^t + 1 where N0 = N_birth - N_adult
That is, take the difference between division rate at birth and division rate as adult and fit a constant k between zero and one. It is just a first approximation at best because data on division rate by age in various tissues doesn't seem available...