Long-Term Clinical Safety of High-Dose Proton Radiation Therapy Delivered With Pencil Beam Scanning Technique for Extracranial Chordomas and Chondrosarcomas in Adult Patients: Clinical Evidence of Spinal Cord Tolerance

High-dose conformal PBSPT may be delivered safely in close proximity to the spinal cord with minimal neurotoxicity. Dose constraints of 64 Gy(RBE) as D2% for the sSC and 54 Gy(RBE) for the cSC seem appropriate for clinical use.