Proton Therapy for Spinal Tumors: A Consensus Statement from the Particle Therapy Cooperative Group.

ABSTRACT

PURPOSE/OBJECTIVES: Proton beam therapy (PBT) plays an important role in the management of primary spine tumors. The purpose of this consensus statement is to summarize safe and optimal delivery of PBT for spinal tumors. MATERIALS/METHODS: The Particle Therapy Co-Operative Group (PTCOG) Skull Base/Central nervous system (CNS)/Sarcoma Subcommittee consisting of radiation oncologists and medical physicists with specific expertise in spinal irradiation developed expert recommendations discussing treatment planning considerations and current approaches in the treatment of primary spinal tumors. RESULTS: CT Simulation Factors that require significant consideration include 1) patient comfort, 2) setup reproducibility and stability, and 3) accessibility of appropriate beam angles. SPINE STABILIZATION HARDWARE If present, hardware should be placed with cross-links well above/below the level of the primary tumor to reduce the metal burden at the level of the tumor bed. New materials that can reduce uncertainties include polyether-ether-ketone (PEEK) and composite PEEK-carbon fiber implants. FIELD ARRANGEMENT Appropriate beam selection is required to ensure robust target coverage and OAR sparing. Commonly, 2-4 treatment fields, typically from posterior and/or posterior-oblique directions, are utilized. TREATMENT PLANNING METHODOLOGY: Robust optimization is recommended for all pencil beam scanning plans (the preferred treatment modality) and should consider setup uncertainty (between 3-7 mm) and range uncertainty (3-3.5%). In the presence of metal hardware, use of an increased range uncertainty up to 5% is recommended. CONCLUSIONS: The PTCOG Skull Base/CNS/Sarcoma Subcommittee has developed recommendations to enable centers to deliver PBT safely and effectively for the management of primary spinal tumors.