Integral dose delivered to normal brain with conventional intensity-modulated radiotherapy (IMRT) and helical tomotherapy IMRT during partial brain radiotherapy for high-grade gliomas with and without selective sparing of the hippocampus, limbic circuit and neural stem cell compartment.

INTRODUCTION: We compared integral dose with uninvolved brain (IDbrain ) during partial brain radiotherapy (PBRT) for high-grade glioma patients using helical tomotherapy (HT) and seven field traditional inverse-planned intensity-modulated radiotherapy (IMRT) with and without selective sparing (SPA) of contralateral hippocampus, neural stem cell compartment (NSC) and limbic circuit.
METHODS: We prepared four PBRT treatment plans for four patients with high-grade gliomas (60 Gy in 30 fractions delivered to planning treatment volume (PTV60Gy)). For all plans, a structure denoted 'uninvolved brain' was created, which included all brain tissue not part of PTV or standard (STD) organs at risk (OAR). No dosimetric constraints were included for uninvolved brain. Selective SPA plans were prepared with IMRT and HT; contralateral hippocampus, NSC and limbic circuit were contoured; and dosimetric constraints were entered for these structures without compromising dose to PTV or STD OAR. We compared V100 and D95 for PTV46Gy and PTV60Gy, and IDbrain for all plans.
RESULTS: There were no significant differences in V100 and D95 for PTV46Gy and PTV60Gy. IDbrain was lower in traditional IMRT versus HT plans for STD and SPA plans (mean IDbrain 23.64 Gy vs. 28 Gy and 18.7 Gy vs. 24.5 Gy, respectively) and in SPA versus STD plans both with IMRT and HT (18.7 Gy vs. 23.64 Gy and 24.5 Gy vs. 28 Gy, respectively).
CONCLUSIONS: In the setting of PBRT for high-grade gliomas, IMRT reduces IDbrain compared with HT with or without selective SPA of contralateral hippocampus, limbic circuit and NSC, and the use of selective SPA reduces IDbrain compared with STD PBRT delivered with either traditional IMRT or HT.