FLASH Particle Radiotherapy

FLASH radiotherapy is an emerging treatment modality characterized by the ultrahigh dose rate delivery of radiation, which has demonstrated the potential to significantly reduce normal tissue toxicity while maintaining tumor control. In cancers traditionally managed with radiotherapy, this approach could improve the therapeutic ratio by mitigating severe side effects associated with current techniques. The integration of particle therapy—such as protons or heavier ions—with FLASH dose rates offers unique physical and biological advantages, including enhanced normal tissue sparing and the possibility of safe dose escalation. Clinical implementation will require a deeper understanding of the mechanistic biological underpinnings of the FLASH effect, alongside advancements in beam delivery systems capable of achieving FLASH dose rates, rigorous quality assurance protocols, and adaptive strategies to accommodate anatomic changes during treatment. Ultimately, widespread clinical adoption will depend on prospective trials comparing FLASH particle therapy with established modalities, with endpoints focused on toxicity, disease control, and patient-reported quality of life.