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Learn More About Proton Therapy

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With Second Mevion Proton System Installed at Siteman Cancer Center, Additional Cancer Patients Begin Treatment

This is Mevion's first staged, 1+1 installation.

LITTLETON, Mass., July 8, 2020 – Mevion Medical Systems announced today that patient treatment has commenced on the MEVION S250i Proton Therapy System® at the S. Lee Kling Proton Therapy Center at Siteman Cancer Center, based at Washington University School of Medicine and Barnes-Jewish Hospital in St. Louis. The new proton therapy system is located directly next to the first system, which was installed in 2013. Mevion is the only proton therapy provider capable of offering a truly modular room-by-room or 1+1 expansion.

Siteman Cancer Center, an NCI-designated Comprehensive Cancer Center, serves patients in Missouri, Southern Illinois, and beyond. Each year, hundreds of cancer patients treated at Siteman have received proton therapy, which is used to treat lung, brain, head and neck, gastrointestinal and gynecologic cancers, and other difficult-to-treat tumors. The growing number of patients treated with proton therapy has increased the need for a second system to accommodate demand.

MEVION S250i Proton Therapy System with HYPERSCAN Pencil Beam Scanning at Siteman Cancer Center, Barnes-Jewish Hospital in St. Louis, MO.

The newest addition to the Kling Proton Center features Mevion’s industry-leading HYPERSCAN® technology and Adaptive Aperture® pMLC. HYPERSCAN provides faster and more precise targeted dose delivery to tumors and minimizes the damage to surrounding healthy tissue and sensitive organs at risk. Siteman has also integrated a high-resolution ceiling-mounted cone-beam CT system and a diagnostic CT on-rail system, enabling a state-of-art Image-Guided Proton Therapy (IGPT) configuration allowing their team to provide adaptive and hypofractionated proton therapy.

“During the past seven years, we have incorporated proton therapy into the treatment plans for hundreds of adult and pediatric cancer patients. Our ability to expand with a second system will enable us to continue to offer the latest technology to more patients and to expand the clinical use of proton therapy,” said Stephanie Perkins, M.D., director, S. Lee Kling Proton Therapy Center.

Scientists from Siteman and Mevion’s Advanced Development team have collaborated on ultra-high dose rate, FLASH therapy research. Last fall, the group successfully delivered over 200Gy/s dose rate on a Mevion production system and published a joint research paper in Medical Physics this May.

“We congratulate Siteman for starting treatment with their second Mevion system,” said Tina Yu, chief executive officer of Mevion Medical Systems. “Mevion is proud to deepen our collaboration with Siteman and look forward to discussing and developing next generation technology and treatment protocols to expand the use of proton therapy on both systems.”

About Mevion Medical Systems

Mevion Medical Systems, Inc. is the leading provider of compact proton therapy systems for use in radiation treatment for cancer patients. Mevion is based in Littleton, Massachusetts, with a presence in Europe and Asia. For more information, please visit

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Melanie Benton

Mevion Medical Systems 1-978-540-1551