Stanford Medicine Cancer Center has completed the first clinical proton therapy treatment delivered inside an existing conventional radiation therapy vault, according to Mevion Medical Systems.
The treatment used the MEVION S250-FIT Proton Therapy System, a compact single-room proton system designed to fit within existing radiation oncology infrastructure.
The system pairs Mevion’s compact fixed-beam proton delivery with Leo Cancer Care’s Marie upright radiotherapy platform.
The configuration removes the rotating gantry and uses 360-degree patient rotation with integrated upright CT imaging, according to Mevion.
Mevion said the S250-FIT reduces the structural footprint to that of a conventional radiation therapy vault and supports image-guided proton therapy within existing infrastructure.
At Stanford, the approach addressed space constraints in Palo Alto and accelerated integration of particle therapy into the existing oncology program, according to the company.
Stanford Medicine opened the proton therapy facility in April 2026 and described it as the first ultracompact proton therapy facility of its kind.
Mevion previously delivered the first S250-FIT system to Stanford Health Care in January 2025 for installation in a conventional linear accelerator vault.
FDA records list the S250-FIT under 510(k) K250986 as a Class II medical charged-particle radiation therapy system.
The device is intended to deliver proton radiation treatment to patients with localized tumors or other conditions susceptible to radiation treatment. When the patient is fully seated, FDA records state that the S250-FIT is indicated for treatment sites above the mid-chest or carina.
Mevion announced in May that the S250-FIT is both FDA-cleared and CE-marked under the European Union’s Medical Device Regulation.
Companies:Mevion Medical Systems, U.S. Food and Drug Administration
Mevion Medical Systems coverage
Sources
- 510(k) Premarket Notification K250986. Regulatory filing
- K250986 510(k) Summary. Regulatory filing
About the author
RadiologySignal.com writersEditorial Team
Radiology Signal Staff covers developments across medical imaging, radiology AI, imaging informatics, clinical research, and radiology business. The team monitors primary sources, peer-reviewed studies, company announcements, society updates, and healthcare industry news to deliver concise reporting for imaging professionals.
