ARE THERE BENEfiTS IN TREATING GLIOBLASTOMAS WITH HYPERARC VERSUS RAPIDARC?

Abstract AIMS This study aimed to compare treatment of frontotemporal glioblastoma using standard planar RapidArc versus non-coplanar radiotherapy (HyperArc). METHODS Ten patients with frontotemporal glioblastoma were retrospectively replanned using HyperArc, maintaining original target volumes and dose constraints. Dosimetric parameters, including PTV coverage and doses to or- gans at risk (OARs), were analysed. Isodose contours (10-60 Gy in 10 Gy intervals) were compared. Additional metrics included conformity index (CI), gradient index (GI), planning and delivery time, and overall cost effi- ciency. RESULTS PTV coverage was comparable across both techniques. HyperArc demonstrated superior plan conformity (median CI: 1.06 vs 1.10) and steeper dose fall-off (median GI: 2.41 vs 2.89). HyperArc significantly reduced radiation expo- sure to normal brain tissue, with notable reductions in V20 (27.8%, ~150 cm³), V30 (26.8%, ~75 cm³), V40 (18.5%, ~30 cm³), and V50 (16.3%, ~15 cm³). Mean brain dose was lowered by 8.7% (from 21.5 Gy to 19.8 Gy). Dose to hair-bearing scalp (≥12 Gy) decreased by 25%. However, HyperArc incurred longer delivery times (~10 minutes vs 3–4 minutes), higher energy demands (one plan required 70% more monitor units), and reliance on Encompass shells. CONCLUSION HyperArc improved plan conformity and decreased the volume of normal brain tissue receiving 20-50 Gy. The mean brain dose was reduced to below 20 Gy, which may help mitigate late neurocognitive effects. Dose to scalp associated with alopecia was reduced by approximately 25%, potentially improving cosmetic outcomes. These dosimetric advantages must be weighed against increased treatment complexity, energy use, and operational de- mands.