Monitoring noise-resonant effects in cancer growth influenced by external fluctuations and periodic treatment

• Published in: The European physical journal. B, Condensed matter physics Condensed matter physics, 2008-10, Vol.65 (3), p.435-442
• Main Authors: Fiasconaro, A., Ochab-Marcinek, A., Spagnolo, B., Gudowska-Nowak, E.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Complex Systems; Condensed Matter Physics; Exact sciences and technology; Fluctuation phenomena, random processes, noise, and brownian motion; Fluid- and Aerodynamics; General aspects; Medical sciences; Physics; Physics and Astronomy; Solid State Physics; Statistical physics, thermodynamics, and nonlinear dynamical systems; Tumors
• ISSN: 1434-6028; 1434-6036
• DOI: 10.1140/epjb/e2008-00246-2

We investigate a mathematical model describing the growth of tumor in the presence of immune response of a host organism. The dynamics of tumor and immune cells populations is based on the generic Michaelis-Menten kinetics depicting interaction and competition between the tumor and the immune system. The appropriate phenomenological equation modeling cell-mediated immune surveillance against cancer is of the predator-prey form and exhibits bistability within a given choice of the immune response-related parameters. Under the influence of weak external fluctuations, the model may be analyzed in terms of a stochastic differential equation bearing the form of an overdamped Langevin-like dynamics in the external quasi-potential represented by a double well. We analyze properties of the system within the range of parameters for which the potential wells are of the same depth and when the additional perturbation, modeling a periodic treatment, is insufficient to overcome the barrier height and to cause cancer extinction. In this case the presence of a small amount of noise can positively enhance the treatment, driving the system to a state of tumor extinction. On the other hand, however, the same noise can give rise to return effects up to a stochastic resonance behavior. This observation provides a quantitative analysis of mechanisms responsible for optimization of periodic tumor therapy in the presence of spontaneous external noise. Studying the behavior of the extinction time as a function of the treatment frequency, we have also found the typical resonant activation effect: For a certain frequency of the treatment, there exists a minimum extinction time.