Modelling Solid Tumor Growth Using the Theory of Mixtures

In this paper the theory of mixtures is used to develop a two-phase model of an avascular tumor, which comprises a solid, cellular, phase and a liquid phase. Mass and momentum balances which are used to derive the governing equations are supplemented by constitutive laws that distinguish the two phases and enable the stresses within the tumor to be calculated. Novel features of the model include the dependence of the cell proliferation rate on the cellular stress and the incorporation of mass exchange between the two phases.A combination of numerical and analytical techniques are used to investigate the sensitivity of equilibrium tumor confixgurations to changes in the model parameters. Variation of parameters such as the maximum cell proliferation rate and the rate of natural cell death yield results which are consistent with analyses performed on simpler tumor growth models and indicate that the two-phase formulation is a natural extension of the earler models.New predictions obtained using the two-phase formulation relate to the impact of mechanical effects on the tumor's equilibrium size which decreases under increasing stress and/or external loading. In particular, as the parameter which measures the reduction in cell proliferation due to cell stress is increased a critical value is reached, above which the tumor is eliminated