FLASH radiotherapy

FLASH radiotherapy is an emerging cancer treatment that delivers a full dose of radiation in an ultra-short burst, at a dose rate of at least 40 grays per second and in under 200 milliseconds, compared with more than a minute for conventional radiotherapy, while killing tumors as effectively as conventional treatment but sparing more of the surrounding healthy tissue. Researchers had initially proposed that the speed of delivery starves tissue of oxygen, but experiments have disproven that theory; current evidence instead points to chemical competition among radiation byproducts in healthy cells and to the fact that far fewer circulating immune cells, roughly 5 to 10 percent compared with 90 to 100 percent under conventional treatment, are affected during FLASH delivery. The first human FLASH treatment took place in 2019 at Lausanne University Hospital, and a 2023 trial using proton therapy in ten patients with bone metastases demonstrated its clinical feasibility, though the treatment is not yet widely available and requires further research and specialized equipment.