An integrated physico-chemical approach for explaining the differential impact of FLASH versus conventional dose rate irradiation on cancer and normal tissue responses

•FLASH radiation dose-rates consume all the local tissue O2 to form reactive organic hydroperoxides.•Fenton type reactions will be limited in normal vs. cancer tissues due to lower levels of labile Fe.•Normal tissues are expected to remove organic hydroperoxides more effectively relative to tumor tissues.•Since tumor tissue cannot remove hydroperoxides as effectively, FLASH and conventional dose rate irradiation are more isoefficient at killing tumor cells compared to normal cells.