On Oct. 22, 2018, the Siteman Cancer Center announced it will open its second proton therapy unit on the Washington University Medical Campus in 2020. Incorporating the latest technology, known as pencil-beam scanning, the system will deliver extremely precise treatments of proton therapy, a type of radiation therapy used to treat cancers in particularly sensitive areas, as well as in children.

Cancer patients in Missouri, Southern Illinois and beyond will have access to a new generation of proton therapy in early 2020. Known as pencil-beam scanning, the technology delivers extremely precise treatments of proton therapy, a type of radiation therapy used to treat cancers of the head, chest, spine and other particularly sensitive areas, as well as pediatric cancers.

Construction will begin in early 2019 next to the region’s only proton therapy system, at Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in St. Louis. The second proton therapy system will complement the first as part of an array of radiation therapy options.

Pencil-beam scanning delivers proton therapy in a single, narrow proton beam aimed directly at the tumor and adjusted for intensity. The beam then “paints” the radiation dose on the tumor. Alternatively, Siteman’s first proton therapy system, available since 2013, precisely targets the tumor using magnets that scatter the proton beam across the tumor. The latter technology will continue to work well for most patients who are candidates for proton therapy, said Jeffrey D. Bradley, MD, the S. Lee Kling Professor of Radiation Oncology at the School of Medicine and director of the S. Lee Kling Proton Therapy Center. Both systems allow for extremely precise adjustments to the radiation beam, so physicians can precisely target tumors while minimizing damage to surrounding tissue.

Both proton therapy units at Siteman are manufactured by Mevion Medical Systems. Other specialized radiation therapy technologies available at Siteman include MRI-guided radiation therapy, CT-guided radiation therapy, Gamma Knife radiosurgery and stereotactic body radiation therapy. All are forms of external beam radiation therapy because the treatments are administered from outside the body. Another type of radiation therapy, brachytherapy, involves implanting “seeds” of radioactive materials next to the tumor. The type of radiation therapy used in a patient’s treatment depends on where cancer cells are located. Washington University radiation oncologists at Siteman select the most appropriate technology based upon a patient’s individual need, unconstrained by equipment availability.