Session Item

It is very well known that tumour environment, in general, and tumour oxygenation, in particular, have a significant impact on the treatment outcome with respect to both local control and long-term prognosis. The reduced oxygen partial pressure in the tumour microenvironment is expected to lead to angiogenesis, but also to restrained proliferation, apoptosis and necrosis, and, overall, to the development of an aggressive phenotype and resistance to treatment. These aspects prompted the extensive study of tumour hypoxia, mostly focusing on correlations between tumour hypoxia prior the treatment and the treatment outcome. Several treatment approaches, techniques and strategies have been proposed and applied aiming at counteracting the expected (chemo)radio-resistance of the tumour cells associated with the presence of tumour hypoxia at the start of the treatment. Tumour hypoxia, however, is not a static feature but a dynamic one, changes in the oxygen availability to the cells being expected to occur during the course of the treatment. This talk will introduce the modelling framework for accounting for changes in tumour hypoxia and hence for modelling the re-oxygenation of the cells. The talk will also present the application of the modelling of tumour oxygenation and re-oxygenation for predicting the probability of controlling the tumour under various scenarios regarding the irradiation procedure involving various radiation qualities, techniques, and fractionation schedules. The theoretical advantage of employing computational models for simulating virtual tumoral systems with respect to their radiobiological environment focusing on the oxygenation and availability of nutrients, while accounting for its dynamic character, will also be presented. The examples emphasizing the role of modelling the re-oxygenation on understanding the outcome of clinical studies will focus on hypofractionated treatments. Finally, the talk will also provide an insight on modelling the changes in the oxygenation of the tumour, and hence the re-oxygenation, based on functional imaging, more specifically based on longitudinal PET imaging sessions with dedicated tracers for tumour hypoxia performed primarily for monitoring the tumour response to radiotherapy.