Abstract: Modification of the biological effect of the absorbed dose and its dependence on the dose rate of ionizing radiation on tumor cells of human lung carcinoma line A 549 is discussed. It is possible to increase the radiosensitization of tumor cells by increasing the absorbed dose by artificially increasing the energy release in the tumor. This can be achieved by introducing or delivering elements into tumor cells with a significantly larger radiation absorption cross-section than that of the biological tissue itself. These are chemical elements with a high atomic number Z, more than 52 (I, Gd, Au, Pt, etc.). Due to the greater probability of interaction of such elements with radiation, it is possible to achieve a local increase in the absorbed dose in the area of their accumulation. A new method of irradiation applied to radiotherapy, called the flash effect, is also discussed, and assumes an ultra-fast (about several tens of milliseconds) dose reduction at a high dose rate, more than 40 Gy /s, compared with the conventional irradiation mode (0.1-0.2 Gy/s). (In connection with the election to fill the position of a senior researcher.)