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An Innovation in Proton Therapy for Central Nervous System Tumors

proton-gantry

At the Johns Hopkins Proton Center, clinicians use sophisticated technology — including CT-guided treatment and a large mechanical arm that can move the proton beam 360 degrees around the patient — to target tumors in critical areas.

April 10, 2020

Johns Hopkins Proton Therapy Center, located at Sibley Memorial Hospital in Washington, D.C., offers cutting-edge treatment for adult and pediatric patients with tumors of the brain and spinal cord. The center’s physicians use the latest pencil beam scanning technology and the precision of image-guided therapy with cone beam CT to target tumors in critical areas while sparing nearby healthy tissue and organs in order to preserve neurocognitive function.

With three clinical gantries and staffed with experts from the Johns Hopkins Kimmel Cancer Center, the proton center specializes in the treatment of brain tumors that abut critical structures such as the brainstem, cochlea, optic pathways and the hippocampus to preserve neurocognitive function and overall quality of life of patients.

“We use the latest proton technology to help reduce both the acute and late radiation-associated toxicities in cases where tumors grow in critical areas,” says Christina Tsien, medical director of the proton center and a leading expert in the treatment of brain tumors.

tsien

“We can use the precision tools of the proton center to help reduce both the acute and late radiation-associated toxicities in cases where tumors grow in critical areas.” — Christina Tsien

Reirradiation with proton therapy is one of the few safe tools available to retreat brain tumors that have progressed following previous treatment. This approach may improve neurologic symptoms and quality of life while providing local control — a potential therapeutic avenue for patients with limited options.

At the Society for Neuro-Oncology, Tsien recently presented research on reirradiation of recurrent glioblastoma, in which patients were treated with a short, hypofractionated radiation in combination with bevacizumab. The study showed that the treatment was safe and well tolerated, and leads to a significant improvement in progression-free survival but without an improvement in overall survival.

Similarly, proton therapy can be used for certain indications including craniospinal radiation in cancers such as pediatric and adult medulloblastoma, ependymomas, other rare tumors and metastatic cancers. 

The Johns Hopkins Kimmel Cancer Center collaborates with Children’s National Hospital, providing photon and proton radiation oncology. The Sibley site treats a wide range of pediatric cancers with radiation therapy. “We want our pediatric patients to maintain a long, healthy life,” Tsien says. “Our focus is on trying to reduce treatment-related complications and providing our pediatric patients with the most state-of-the-art technologies.”

Johns Hopkins’ latest proton technology also includes respiratory-gated real-time fluoroscopy, which accounts for patient movement and ensures that the pencil beam scanning is only turned on when the tumor and the proton beam are aligned. Precision alignment further reduces the radiation dose to healthy tissue, helping to spare critical structures including heart, lungs and other abdominal structures. 

Tsien’s own research on glioblastoma, low-grade brain tumors and brain metastases dovetails well with her work at the proton center. “My research has been on novel MR and PET imaging biomarkers to help understand biologically where the most active part of the tumor is,” she says, “and being able to use this information to target the most aggressive areas of the tumor with proton therapy is of great interest.”


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