LITTLETON, Mass. — Mevion Medical Systems, Leo Cancer Care and RaySearch Laboratories will highlight upright proton therapy at the American Society for Radiation Oncology 2026 Annual Meeting, following the first reported treatment of a patient in an upright position using the MEVION S250-FIT Proton Therapy System.
Stanford Medicine reported treating the first patient upright on June 4, 2026, using Mevion’s S250-FIT system with Leo Cancer Care’s Marie upright positioning and imaging system and RaySearch’s RayStation treatment planning software. The system was installed within a standard radiation therapy vault.
At ASTRO 2026 in Boston, attendees will be able to see and experience the upright positioning system and speak with therapists and physicists involved in positioning patients for treatment.
Proton therapy has longstanding ties to Boston. Harvard physicist Robert R. Wilson proposed using the Bragg peak to treat cancer in 1946. Fifteen years later, Harvard’s cyclotron and Massachusetts General Hospital began treating patients in a partnership that continued for decades.
Mevion Medical Systems was founded in Massachusetts in 2004 with the goal of expanding access to proton therapy. Its MEVION S250 Proton Therapy System received FDA clearance in 2012 as a compact proton therapy system.
In 2025, the MEVION FIT system received FDA clearance. The system is designed to fit within an existing linear accelerator, or LINAC, vault.
Mevion said the approach could allow radiation oncology departments to add proton therapy within existing infrastructure. About a dozen FIT systems are currently in development worldwide, according to the company.
“Every health system should be able to offer proton therapy as part of its radiation oncology service,” said Tina Yu, Ph.D., President and CEO of Mevion Medical Systems. “With patients being treated in an existing department, the conversation can finally focus on how proton therapy fits into a health system’s clinical service, facilities and capital planning.”
The FIT platform combines Mevion’s compact proton accelerator and HYPERSCAN pencil beam scanning technology with Leo Cancer Care’s Marie 360-degree upright patient positioning system and integrated CT imaging. Treatment planning is provided through RaySearch Laboratories’ RayStation system.
The platform also includes Mevion’s Adaptive Aperture technology for beam shaping. The companies said they will also discuss future technologies at ASTRO, including DirectARC proton arc therapy and adaptive treatment workflows.
Leo Cancer Care has developed upright patient positioning and imaging technologies for radiation therapy, with systems in clinical and research use internationally.
“Our work is to help clinical teams bring upright imaging and positioning into daily practice,” said Stephen Towe, CEO of Leo Cancer Care. “At ASTRO, we want therapists, physicists and physicians to experience the setup and discuss the practical questions that matter in their departments.”
RaySearch Laboratories develops treatment planning software for particle therapy. Its RayStation platform is now being used clinically for upright proton therapy at Stanford Medicine.
“We are proud to have contributed to the first proton treatments at Stanford Medicine together with Mevion and Leo Cancer Care,” said Johan Löf, Founder and CEO of RaySearch Laboratories. “Through the close integration of the three systems, we have shown that RaySearch’s advanced and well-established proton therapy algorithms deliver high performance also when treating patients in the upright position.”
