Dear Colleagues,

External beam radiotherapy (RT) is a treatment option for cancer patients. More than half of patients benefit from combining radiation therapy (RT) with other treatment modalities such as chemotherapy, surgery, and recently immunotherapy to improve the treatment index. The target organs are irradiated for different field sizes in this machine, depending on the tumor volume. This technology has early and late side effects such as producing secondary photoneutrons in healthy (non-tumor) tissues, fatigue, skin problems, and hair loss.  The side effects are dependent on the type of cancer, its location, the radiation therapy dose, general health, and other factors. In order to overcome the possible risks in out-of-field organs, the novel technology of RT, dubbed FLASH radiation therapy piqued the interest of many researchers. This modality exploits a high dose rate of radiation in a fraction of a second. In comparison to conventional RT, FLASH-RT achieves the maximum curative dose to the target organ and has a non-toxic nature in normal tissues, opening up avenues for cancer treatment. FLASH-RT has a much higher dose rate (>40Gy/s) and is also faster (nanoseconds-microseconds) than routine conventional RT practice. In this section, Researchers are invited to present new research ideas in the radiotherapy field especifically FLASH-RT to reduce the possible risks in out-of-field organs.  Research articles, technical reports, and reviews in this area of study are welcome.