Characteristics of cube root growth of transplantable tumours

Abstract

A general method for calculating a mean generation time with an account of the variation of individual generation time is developed. It was achieved through formulation of a stochastic model which is a generalization of the “multiple-phase birth process” (Kendall, 1948a). By the application of this method, it is confirmed that “cube root growth.” is characterized by progressive lengthening of mean generation time at a constant rate (deceleration rate). The deceleration rate depends solely upon the coefficient of variation (C.V.) of individual generation time. The parameters explicit in the growth equation is found to affect the initial value of the mean generation time alone. Insofar as the C.V. of generation time is not far from the reported range, i.e. 20 to 26%, the “deceleration rate” is always about six hours per day. The implication of growth fraction is also discussed.