In addition to surgery, radiotherapy and chemotherapy are the two most common anticancer treatments used to treat cancer. The effectiveness of these anti-cancer treatment protocols is considerably affected by both intracellular and extracellular heterogeneities as well as by the dynamical changes within the tissue microenvironment. Hence, it is important to consider such spatio-temporal heterogeneities and changes when studying the effects of these treatments and their optimised scheduling, as this can help in improving the delivery of multimodality treatments.

The spatio-temporal changes in the intracellular cell-cycle dynamics and variations in microenvironment oxygen levels play a vital role in mediating a cell’s sensitivity and response to the radiation therapy. Moreover, in addition to tumour control, the ionizing radiation indirectly induces other local and nonlocal bystander effects whose consequences are poorly characterised but which will certainly include secondary malignancies (metastases). Here, we consider a hybrid multiscale mathematical and computational model to study the direct effects of radiation as well as radiation-induced bystander effects on a tumour growing within host tissue. We use the model to study the role of radiation-induced bystander effects when tumour cells are treated with different therapeutic schedules and analyse their clinical and diagnostic implications.