There are different molecular aspects of the mechanisms for the radioresistance of tumors, including intrinsic genetic or epigenetic changes in cancer cells, the microenvironment of tumors, the existence of a small number of radioresistant cancer stem cells, etc. Recently, a series of reports have suggested that M6A modifications are critical mechanistic responses of cells to irradiation and contribute to clinical outcomes of cancer radiotherapy [64,65]. This evidence concerns the gene METTL3 and cancer.