The Molecular Mechanisms of the FLASH Effect in Radiobiology

The use of ionizing radiation at an ultra-high dose rate (≥40 Gy/s), which is called FLASH irradiation, contributes to the preservation of healthy tissues with a level of tumor control comparable to that of irradiation at a standard dose rate. This review summarizes the current knowledge obtained in studies of irradiation of tumor and normal cell lines and animals, including tumor carriers, in conventional and FLASH modes. For comparison, data on FLASH irradiation with photons, electrons, and protons, as well as ions of helium and carbon, are also provided. The biophysical, molecular biological, and immunological aspects of FLASH exposure necessary for understanding radiation-induced processes in cells and tissues in order to improve tumor radiotherapy are discussed.