Littleton, Mass. — Mevion Medical Systems said Stanford Medicine Cancer Center in Palo Alto, Calif., has delivered the first clinical treatment using the company’s MEVION S250-FIT Proton Therapy System.
The treatment marks the first clinical use of an ultra-compact proton therapy system installed inside an existing conventional radiation therapy vault, the company said.
Mevion said the system is designed to reduce the space and infrastructure requirements that have historically limited adoption of proton therapy, which often requires dedicated facilities or large shielded bunkers.
The MEVION S250-FIT combines Mevion’s compact fixed-beam proton delivery technology with Leo Cancer Care’s MARIE platform, which provides 360-degree patient rotation and integrated upright CT imaging. The system removes the need for a rotating gantry and is designed to fit within a conventional radiation therapy vault.
For Stanford Medicine, Mevion said the system helped address space constraints in Palo Alto and allowed the cancer center to add proton therapy to its existing oncology program.
“Today’s milestone marks a turning point, not only for Mevion, but for the broader radiation oncology community,” said Tina Yu, Ph.D., CEO and President of Mevion Medical Systems. “We have validated a new class of ultra-compact proton therapy: a modular alternative to conventional X-ray linacs that fundamentally changes the equation around space, cost, and access. By removing the infrastructure barriers that have historically defined this field, we are helping more health systems bring proton therapy to their patients.”
Dr. Yu continued: “This platform is also built for what comes next. The MEVION S250-FIT™ is designed to support DirectARC™, daily online adaptive proton therapy, FLASH novel treatment techniques, and continued advances in robustness and LET optimization, the capabilities that will define the next decade of clinical proton therapy.”
The Stanford project was supported by Stantec, NELCO and RaySearch. Mevion said the S250-FIT system is FDA-cleared and CE-marked.
The company said additional installations are expected in 2026 and beyond across North America, Europe and Asia, including projects with BayCare, Atlantic Health System, University of Nebraska Medical Center, Loma Linda University Medical Center, UNC Health, Dana-Farber Cancer Institute, Istituto Nazionale Tumori IRCCS Fondazione G. Pascale and Tam Anh General Hospital Partner.
