RADT-05. VOLUMETRIC MODULATED ARC THERAPY CRANIOSPINAL IRRADIATION UTILIZING A VERTEBRAL BODY SPARING APPROACH: A DOSIMETRIC ANALYSIS

Abstract BACKGROUND Craniospinal irradiation (CSI) is indicated for adult patients diagnosed with leptomeningeal disease (LMD). Proton-based vertebral-body-sparing (VBS) CSI has been explored pediatric to minimize hematologic toxicity; however, utilization of VBS in an population limited. We hypothesize that VBS-CSI utilizing volumetric modulated arc therapy (VMAT) will effectively reduce vertebral body dose while minimizing surrounding organs-at-risk (OAR) LMD. METHODS Ten LMD received CSI, 30 Gy 10 fractions. These were initially treated a variety VMAT and IMRT treatment techniques. then retrospectively replanned using VBS-CSI. For their replan, full arcs the brain fields matched two spine isocenters upper lower created limited posterior arcs. The PTV was margins 3mm uniformly around contour 7mm spinal canal. To further decrease dose, avoid entry exit created. This structure margin on anteriorly designed carve out bodies still maintaining coverage PTV. RESULTS All had reduction when compared initial plan. mean plans average 33% plans. small bowel esophagus reduced by 46% 67%, respectively. CONCLUSIONS may be utilized OARs bodies. In this study, led significant reductions also other OARs. acceptable alternative proton-based Prospective evaluation warranted.