Proton Beam Therapy

The S. Lee Kling Proton Therapy Center at Siteman Cancer Center. The S. Lee Kling Proton Therapy Center at Siteman Cancer Center.

The S. Lee Kling Proton Therapy Center at the Siteman Cancer Center is one of the only proton therapy centers located within a 240-mile radius of St. Louis.

The center houses two proton units: the world’s first compact proton beam accelerator, called the Mevion S250™ Proton Beam Therapy System, as well as a second unit equipped with pencil-beam scanning technology.

Radiation oncologists and physicists here helped evaluate the original system, the Mevion S250, and developed the patient protocols and quality standards for this advanced proton treatment technology.

Both systems allow for extremely precise adjustments to the radiation beam, so physicians can precisely target tumors while minimizing damage to surrounding tissue.

Proton beam therapy’s main advantage is that proton radiation specialists can control radiation beams by:

  • Depth
  • Shape
  • Amount of radiation dose

In other external radiation therapies, radiation beams pass through a patient to a defined location and then exit the body on the other side, leaving deposits of radiation all along their path. Because proton radiation therapy allows for depth control, the majority of radiation is held until the proton beams hit the precise area targeted. Little to no radiation is delivered past the tumor.

Proton therapy cancer treatment can be used as a solo treatment option or it can be used in combination with other radiation therapies or chemotherapy.

There are only a handful of proton beam therapy centers in the United States, most with large, football field-sized treatment areas. In contrast, the Mevion S250™ system, called a superconducting synchrocyclotron proton accelerator, is much more compact, fitting into about 2,000 square feet. The compact nature of the technology makes it more versatile as well as more cost-effective to use.

The Mevion S250 system, which debuted in late 2013, is ideal for patients with solid tumors that are located near sensitive structures or tissues, such as the eyes, brain or spinal cord. It is particularly beneficial for children, where precise targeting is critical to avoid impacting growing bones or tissues. St. Louis Children’s Hospital and the Siteman Cancer Center are committed to providing proton beam therapy in a way that is sensitive to the needs of children and their families.

Pencil-beam scanning technology

This technology is the most advanced form of radiation therapy available, as it delivers extremely precise treatments of proton therapy.

Installation of this second unit began in early 2019 and was completed in June 2020.

“Pencil-beam scanning helps us provide patient-specific care for adults and children, particularly those who have especially complicated cases,” said Stephanie M. Perkins, MD, director of the Proton Therapy Center and an associate professor of radiation oncology at Washington University.

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 onto the tumor.