Combined Radio-Chemotherapy Model Using Coupled Differential Equations

Combined radio-chemotherapy aims to exploit the complementary action of irradiation and systemicpharmacological treatment. In this work, a coupled differential equation model is proposed in whichtumor growth is opposed simultaneously by a radiotherapy term and a chemotherapy term. The modelincludes a logistic growth equation for tumor burden and a first-order elimination equation for drugconcentration. Analytical developments are performed for the linearized regime, cumulative treatmenteffects, and effective net growth reduction. The framework illustrates how coupled ordinary differentialequations can represent combined oncological interventions in a simple but expressive mathematical form.