November 2, 2021 — Varian, a Siemens Healthineers company, and the Cincinnati Children's/UC Health Proton Therapy Center announced the completion of enrollment in FAST-01 (FeAsibility Study of FLASH Radiotherapy for the Treatment of Symptomatic Bone Metastases), the first human clinical trial of FLASH therapy.
The FAST-01 trial, which is evaluating clinical workflow feasibility of the FLASH therapy and treatment-related side effects, met its enrollment target of 10 participants with bone metastases in the extremities. The clinical trial, informed by years of preclinical work, was designed by experts at Varian and multiple centers in the FlashForward Consortium, including Cincinnati's Children's/UC Health Proton Therapy Center and the New York Proton Center.
The FAST-01 trial is being led by John C. Breneman, M.D., principal investigator, and Medical Director of the Cincinnati Children's/UC Health Proton Therapy Center, UC Health radiation oncologist, and professor emeritus at the University of Cincinnati College of Medicine. "The completion of enrollment brings the clinical community one step closer to making an informed evaluation of FLASH therapy," said Breneman. "The team is looking forward to reviewing and sharing the findings, while also looking ahead toward the next clinical phase of research," he added.
The trial is supported by Emily Daugherty, M.D., assistant professor of radiation oncology at UC and a UC Health radiation oncologist, and Anthony Mascia, PhD, DABR, adjunct assistant professor of radiation oncology at UC and Director of Medical Physics at the Cincinnati Children's/UC Health Proton Therapy Center.
"Clinical trial investigators have worked diligently to complete enrollment of FAST-01 over the last year. Achieving this significant milestone is a vital step forward to demonstrating the feasibility of using FLASH therapy in a clinical setting and not just in a laboratory," said Agam Sharda, Vice President of Flash Solutions at Varian. "We are grateful to the trial subjects who, by virtue of their participation, have contributed to the advancement of FLASH technology, for the potential future benefit of others who may one day need to undergo treatment for cancer."
"Initial findings indicate that the Varian ProBeam system, modified to deliver FLASH therapy, is performing as planned during the study. To date, none of the trial participants have suffered any serious adverse events related to FLASH," said Ricky Sharma, M.D. Ph.D., Vice President of Clinical Affairs at Varian. "There is still much work and research to be done, and we are eager to explore all the clinical trial data."
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For more information: www.varian.com
November 13, 2025 
