# Very-high-energy electron therapy

Source: https://onco.cc/technologies/vhee-radiotherapy/  
OnCo record `vhee-radiotherapy` (Technology). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

VHEE radiotherapy fires electrons at 100 to 250 MeV, energies that reach deep tumours and can be steered by magnets, aiming to deliver FLASH-speed radiation from a machine smaller and cheaper than a proton facility. It is still at the accelerator-development and preclinical stage: no patient had been treated by September 2026.

## Summary

Electrons in the 100-250 MeV range penetrate deeply, are steerable by magnets, and can be delivered at the ultra-high dose rates associated with the FLASH effect, in principle for a fraction of the cost of a proton facility. Work is at the accelerator-development and preclinical stage at CHUV/CERN, SLAC and elsewhere; the FLASH studies that exist in humans use conventional-energy electrons for skin lesions (for example NCT06549439, completed) or protons. No VHEE patient treatment had been reported by September 2026.

## Fields

- Kind: Technology
- Status: preclinical
- Last checked: 2026-09-08
- Tags: frontier; radical
- Principle: Very-high-energy electrons deposit a relatively flat depth dose that can be shaped magnetically, enabling deep targets and millisecond delivery.
- Strengths: Potential FLASH sparing at depth; Magnetic scanning is fast and precise; Cheaper and smaller than proton or carbon facilities
- Limitations: No clinical machine yet; Dosimetry at ultra-high dose rate is unsolved; FLASH sparing itself remains unproven in humans

## Sources

- eFLASH skin melanoma study (NCT06549439): https://clinicaltrials.gov/study/NCT06549439

## Connected records

- fronts: [Radiation Therapy](https://onco.cc/fronts/radiation/)
- technologies: [Carbon-ion therapy](https://onco.cc/technologies/carbon-ion/), [FLASH radiotherapy](https://onco.cc/technologies/flash-rt/), [IMRT / IGRT (modern external beam)](https://onco.cc/technologies/imrt-igrt/), [Proton therapy](https://onco.cc/technologies/proton-therapy/)
- roadmaps: [Radical oncology: what could change the war by 2035](https://onco.cc/roadmaps/frontier-2035/), [Radiotherapy roadmap: X-rays → shaped beams → fewer fractions, particles and FLASH](https://onco.cc/roadmaps/radiation-roadmap/)

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