# FAST-01 (proton FLASH for bone metastases)

Source: https://onco.cc/trials/fast-01/  
OnCo record `fast-01` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

The first clinical trial of ultra-fast proton radiotherapy, in ten patients with painful bone metastases in the limbs. Treatment ran without technical problems and side effects were like those of ordinary radiotherapy.

## Summary

FAST-01 treated 10 patients at 12 sites with a single transmission proton beam at 40 Gy per second or more on a FLASH-enabled Varian ProBeam, prescribing 8 Gy as in standard palliative care. There were no FLASH-related technical problems or delays; average time on the couch was 18.9 minutes per patient. Adverse events were mild and consistent with conventional radiotherapy, and transient pain flares occurred. It established workflow feasibility, not a tissue-sparing benefit.

## Fields

- Kind: Trial
- Status: completed
- Last checked: 2026-11-04
- Also known as: FAST-01 trial; Feasibility Study of FLASH Radiotherapy for the Treatment of Symptomatic Bone Metastases
- Tags: machines-wave3
- Registry id: NCT04592887
- Phase: not-applicable
- Setting: Adults with one to three painful bone metastases in the arms or legs, treated with a single 8 Gy proton FLASH fraction at Cincinnati Children's/UC Health Proton Therapy Center
- Sponsor: Varian, a Siemens Healthineers Company
- Enrolled: 10
- Result: Proton FLASH was delivered without technical issues in 10 patients; side effects were mild and similar to conventional radiotherapy.

## Sources

- ClinicalTrials.gov NCT04592887: https://clinicaltrials.gov/study/NCT04592887
- Mascia et al., proton FLASH for symptomatic bone metastases: the FAST-01 trial (JAMA Oncology 2023): https://doi.org/10.1001/jamaoncol.2022.5843

## Connected records

- technologies: [FLASH radiotherapy](https://onco.cc/technologies/flash-rt/), [FLASH research accelerators (Oriatron, Mobetron FLASH, ProBeam FLASH)](https://onco.cc/technologies/flash-research-accelerators/), [Proton therapy machines: cyclotrons, synchrotrons and single-room systems](https://onco.cc/technologies/proton-therapy-systems/)
- companies: [Varian (Siemens Healthineers)](https://onco.cc/companies/varian/)
- terms: [Bone metastases and skeletal-related events](https://onco.cc/terms/bone-metastases/)
- trials: [FAST-02 (proton FLASH for thoracic bone metastases)](https://onco.cc/trials/fast-02/)
- roadmaps: [Particle therapy machines: from Loma Linda to proton rooms in a linac vault, carbon gantries and FLASH](https://onco.cc/roadmaps/particle-therapy-machines-roadmap/)

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