GOMPERTZIAN REEVALUATION OF THE GROWTH-PATTERNS OF TRANSPLANTABLE MAMMARY-TUMORS IN SIALOADENECTOMIZED MICE

The method of the recursion formula of the Gompertz function (Bassukas & Maurer-Schultze 1988) has been applied to analyse tumour growth dat a taken from the literature; namely the growth perturbation of transpl antable mammary tumours in sialoadenectomized mice with or without sub sequent epidermal growth factor substitution (results on two mouse str ains, C3H or SHN, have been reported; Inui, Tsubura & Morii 1989). The recursion formula of the Gompertz function fits growth curves to all seven sets of data well (P > 0.05 for lack of fit test). The growth pa ttern of the tumours in the unperturbed hosts is Gompertzian and does not change if tumours are transplanted in sialoadenectomized mice, alt hough the starting specific growth rate decreases in C3H mice. However , if sialoadenectomy is carried out after tumour inoculation, a comple x alteration of the tumour growth evolves: tumour growth does not simp ly decelerate but it also shifts from the conventional Gompertzian to an exponential or even 'hyperexponential' growth pattern, i.e. with an accelerating specific growth rate. Some theoretical mechanisms of thi s alteration, as well as the differences between the present Gompertzi an analysis and a previously published Verhulstian analysis of part of the same data (Leith, Harrigan & Michelson 1991), are discussed. It i s concluded that the quantitative analysis of tumour growth patterns b y the method of the difference equation of the Gompertz function prese ntly applied may substantially contribute to the improvement of the in terpretation of perturbations of tumour growth-irrespective of their g enesis. In contrast to the application of some a priori fixed growth f unction, e.g. the Verhulstian one, the present method can quantitative ly interprete different growth patterns and their classification on th e basis of linear regression analysis.