Thanks to numerous technological advances, radiation therapy has become a standard of care in cancerology. However, the efficacy of conventional radiation therapy (CRT) is limited by the damage it may do to healthy neighboring tissues. To address this issue, recent research in radiation oncology has led to the development of ultra-high dose rate "FLASH" radiotherapy (FRT), a novel radiation technique involving the delivery of fast bursts (a few milliseconds) of radiation doses calculated to destroy cancer cells but leave neighboring cells unaffected. Several studies have confirmed that FRT is efficacious against a number of solid tumors while also being relatively innocuous for the surrounding tissues. Among them was a clinical study¹ wherein a first patient was treated with FRT, thus demonstrating the clinical feasibility of the technique.

Researchers from CEA-Jacob, in collaboration with the Lausanne University Hospital CHUV, analyzed the effects of FLASH-RT on acute lymphoblastic leukemia and normal hematopoiesis in an animal model with xenografts. The results show that FLASH-RT delays the spread of leukemia more effectively than NSCLC-RT in a particular genetic subtype.

This work provides novel information suggesting that FRT has advantages over CRT for the treatment of children with certain subtypes of T-ALL and furthermore preserves some of the properties of normal blood stem cells in that setting. Their work is an example of the "FLASH effect" (efficacy against tumors; innocuousness for healthy tissues), which will surely bring great benefits to patients once it arrives in the clinic. That arrival however is dependent on the development of pertinent radiological equipment for the clinic.