Radiobiology 2016

Different mechanisms of reoxygenation

1. Classic: preferential killing of well-oxygenated cells, and the surviving hypoxic cells getting access to O 2 . Caveat: it takes time for cells to physiologically die, even after several divisions, and in human tumors this may take several days. 2. Reoxygenation due to acute/cycling hypoxia. Based on changes in perfusion (min-hours) and vascular function/remodelling (hours-days). 3. Reoxygenation due to reduced energy metabolism. Occurring rapidly and detectable by nitroimidazole PET or IHC markers. Caveat: reoxygenated cells after irradiation may be clonogenically dead (but they don’t know it yet).