The effect of time ordering and concurrency in a mathematical model of chemoradiotherapy

We study the effect of switching the order of administration of cytotoxic drugs and radiation in cancer therapy by comparing a sequential and a concurrent protocol of chemoradiation. For this purpose, we derive a nonlinear ordinary differential equation model based on well-accepted knowledge of chemotherapy and radiotherapy for in vitro solid tumors. Using the bifurcation theory, we demonstrate that the administration of radiotherapy concurrently, once the chemotherapeutic regime has caused a considerable reduction of the tumor burden, might be more pertinent than the reverse strategy in those circumstances where bistability occurs. Consequently, our analysis suggests that an adequate time order and concurrency may have potential benefits in chemoradiation of solid tumors. (c) 2021 Elsevier B.V. All rights reserved.