FLASH Radiotherapy (for Medical Linear Accelerators)
A fast-moving frontier that could widen the therapeutic window
FLASH radiotherapy (FLASH-RT) delivers the total radiation dose at ultra-high dose rates — in a fraction of a second. Preclinical studies have shown a remarkable “FLASH effect”: similar tumour control to conventional radiotherapy but substantially reduced damage to normal tissues. This makes FLASH one of the most promising innovations in radiotherapy in recent years.
Why it matters
If FLASH-RT can be reliably reproduced in humans, it could let clinics give higher effective tumour doses or reduce side effects for current regimens — potentially changing how we treat radio-sensitive organs or large-volume disease. Early human treatments using modified LINACs and ongoing clinical trials demonstrate growing interest.
Key technical and clinical challenges
Delivery hardware: Conventional LINACs must be modified or redesigned to deliver the ultra-high instantaneous currents and pulse structures required for FLASH. Electron beams have shown feasibility, but their shallow penetration limits some tumour sites. Very-high-energy electrons and novel photon approaches are under active investigation.
Dosimetry & QA: Measuring dose and dose rate at ultra-high levels requires new detectors, calibration methods, and quality assurance workflows.
Biological mechanisms & translation: The precise biological basis of the FLASH effect is still being defined. This uncertainty makes dose scheduling and patient selection ongoing research areas.
Opportunities & near-term directions
LINAC adaptation: Modified clinical accelerators and compact electron accelerators are being developed for first-in-human treatments.
Hybrid regimens: Combining FLASH fractions with conventional photon treatments could make benefits accessible sooner while overcoming technological hurdles.
Standardization: To move beyond pilot studies, standardized QA protocols and reproducibility studies are essential, along with cost and maintenance planning for widespread use.