Mathematical modeling of tumor growth as a random process in the presence of interaction between tumor cells and normal cells

A mathematical model of tumor growth as a random process is studied, in which there is an interaction between tumor cells and normal cells. A set of two coupled stochastic differential equations defines the dynamics of tumor cells and normal cells. The evolution contains driven growth, therapy, and Gaussian white noises terms. The corresponding Fokker-Planck equation is used to study the large-time behavior of the system. Specifically, for periodic therapy terms, the ratio of the probability of large tumor cells number to the probability of small tumor cells number is investigated. It is seen that increasing the interaction between the tumor cells and normal cells decreases this ratio.