RecruitingRadiation therapyProton SBRT for Spinal MetastasisThis is a single-arm pilot study of proton stereotactic body radiotherapy (SBRT) for nonhematologic spinal metastasis in patients with complex lesions that are unable to be effectively treated with standard of care photon SBRT defined as inability to develop a photon SBRT plan that achieves adequate coverage (≥80% planning treatment volume (PTV) coverage)) with a prescription dose of 30 Gy in 5 fractions.