Modeling and analysis of nonlinear tumor‐immune interaction under chemotherapy and radiotherapy.

This paper examines the effects of treatment on tumor‐immune dynamics based on a conceptual two‐dimensional model. In absence of treatment, this model exhibits regimes of "active" and "dormant" tumor. Increasing intensity of chemotherapy entails a significant complication of tumor‐immune interaction with parameter zones of monostability, bistability, and tristability where "active," "dormant," and "zero" tumor states can coexist. A detailed description of bifurcations, attractors, and their basins is given. Based on this mathematical analysis, we discuss efficiency of various programs of treatment combining chemotherapy and radiotherapy. [ABSTRACT FROM AUTHOR]