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First-in-Human FLASH Radiation Therapy Trial Deemed a "Breakthrough"

Aug 22, 2023, 15:53 PM by Nyla Sauter

Physics World names FAST-01 trial a Top 10 Breakthrough, and USA Today proclaims it one of the Top 3 Advances in Cancer Treatment. 

Proton Therapy Center

Research findings from the world’s first-in-human clinical trial of proton FLASH therapy, which was conducted at the Cincinnati Children’s/University of Cincinnati Medical Center Proton Therapy Center, indicate the clinical feasibility and preliminary efficacy and safety of an experimental treatment for cancer patients that delivers radiation therapy at ultrahigh dose rates in less than 1 second. 

FLASH radiotherapy induces a phenomenon known as the FLASH effect, which reduces harm to normal tissue surrounding a tumor during conventional radiation therapy while still killing the cancer cells at the tumor site. 

“Our unique FLASH research has far-reaching implications for how we treat cancer in kids and adults,” says John Perentesis, MD, senior advisor at the University of Cincinnati Cancer Center, research director for the Proton Therapy Center, and co-director of the Cancer and Blood Diseases Institute at Cincinnati Children’s. “It’s important because radiation is one of the most effective tools for treating cancer and is used for nearly half the cancer patients in the U.S. FLASH holds promise to become a paradigm-shifting technology by potentially providing more effective cancer treatment with fewer side effects.” 

The FAST-01 study was led by Cancer Center members John Breneman, MD, medical director of the Proton Therapy Center, and Emily Daugherty, MD, a clinical/ translational researcher at the Cancer Center and assistant professor in the UC College of Medicine. Findings were published in JAMA Oncology and presented Oct. 23, 2022, at the American Society for Radiation Oncology (ASTRO) annual meeting. Anthony Mascia, PhD, chief physicist at the Proton Therapy Center, is the principal author of the landmark JAMA Oncology paper. 

Data from FAST-01 has already led to the approval of FAST-02. The FAST-02 clinical trial (FeAsibility Study of FLASH Therapy for the Treatment of Symptomatic Bone Metastases) is expected to enroll 10 patients with painful bone metastases. The study aims to evaluate treatment-related side effects and efficacy of treatment, which will be assessed by measuring trial participants’ pain relief. 

“Our study shows FLASH radiotherapy with protons is a practical modality to reduce pain,” says Daugherty. “It deserves further exploration because of its potential to decrease the side effects associated with conventional radiation treatments.” 

FLASH RT vs. Conventional Radiotherapy for Bone Metastases
   FLASH RT  Conventional Radiotherapy
Radiotherapy Dosage  FLASH-enabled (≥40 Gy/sec) proton radiotherapy system using a single-
transmission proton beam 

Conventional dose rate is approximately 0.03 Gy/sec but can vary by patient  

Time on
Treatment Table

15.8 minutes per treated site 

15-30 minutes
Delivery Time of Treatment 3/10 of a second
A few minutes

Number of Treatments
 1 Can be 1, but often requires treatment 5 days a week for 2-3 weeks, depending on the size, type and location of the cancer 
Side Effects  

Mild with most common being transient
mild skin hyperpigmentation 


Varies by location of radiation but can include damage to nearby cells and tissue, fatigue, skin changes and issues like weight loss and hair loss 

Pain Reduction  

8 out of 12 treatment sites for an overall response rate of 67% 


65% overall response rate achieved in the RTOG 9714 trial