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Siteman Cancer Center Begins Treatment with Latest Mevion Proton Therapy System
[November 16, 2023]

Siteman Cancer Center Begins Treatment with Latest Mevion Proton Therapy System

Mevion Medical Systems announced today that the world's first single-room proton therapy system has completed the upgrade to the latest MEVION S250i Proton Therapy System® with FLASH* capabilities, and has begun treating patients in November at the S. Lee Kling Proton Therapy Center at Siteman Cancer Center, Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis, MO.

This press release features multimedia. View the full release here:

The MEVION S250i Proton Therapy System (Photo: Business Wire)

The MEVION S250i Proton Therapy System (Photo: Business Wire)

Siteman Cancer Center is an NCI-designated Comprehensive Cancer Center that draws patients from Missouri, Southern Illinois and beyond. The center utilizes Mevion's modular 1+1 expansion configuration and is now equipped with two MEVION S250i systems for treating a wide range of pediatric and adult indications, including lung, brain, head and neck, gastrointestinal and gynecologic tumors, and other complex cases.

Tina Yu, Ph.D., CEO and President of Mevion Medical Systems, expressed her delight: "We could not be more excited for Siteman and the treatment of its first patient on the second MEVION S250i systm. We are proud of our collaboration."

Proton therapy is a precise form of radiation therapy that can reduce the amount of unnecessary radiation exposure to surrounding healthy tissue and sensitive organs at risk. The first patient treated is a young adult with breast cancer who will receive less radiation to surrounding healthy tissues and organs such as the heart and lungs, thus reducing long term toxicities.

"Our recent system upgrade allows for the provision of advanced technology to an even greater number of patients, especially pediatric and young adult cases, and allows us to expand the clinical applications of proton therapy," said Stephanie Perkins, M.D., Professor and Director of S. Lee Kling Proton Therapy Center. "Our team also looks forward to advancing FLASH dosimetry research."

This latest system incorporates Mevion's cutting-edge HYPERSCAN® Pencil Beam Scanning for Intensity Modulated Proton Therapy (IMPT) with a proton MLC, along with an advanced 3D imaging system for high-precision Image-Guided Radiation Therapy (IGRT) and adaptive therapy. Additionally, the system is capable of delivering ultra-high FLASH dose rate for research and development. These latest capabilities are the result of a collaborative effort between Mevion and Siteman Cancer Center, initiated in 2019.

The FLASH therapy technique, which delivers an ultra-high dose rate of therapeutic radiation in under a second without any invasiveness, possesses the potential to significantly enhance the efficacy of cancer treatments while simultaneously reducing side effects and shortening treatment duration.

*FLASH therapy is not yet available for clinical use.

About Mevion Medical Systems

Mevion Medical Systems is the leading provider of compact proton therapy systems for cancer care. Dedicated to advancing the design and accessibility of proton therapy worldwide, Mevion pioneered the single-room platform and continues to further the science and application of proton therapy. Since 2013, Mevion compact proton therapy single-room systems have been used by leading cancer centers for treating patients. Mevion's series of products, including the flagship MEVION S250i and MEVION S250-FIT* with HYPERSCAN pencil beam scanning, represent the world's most compact proton therapy systems that eliminate the obstacles of size, complexity, and cost. Mevion is headquartered in Littleton, Massachusetts with a presence in Europe and Asia. For more information, please visit

*The MEVION S250-FIT Proton Therapy System™ is not yet available for clinical use.

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