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. 2016 Sep 8;11(1):118.
doi: 10.1186/s13014-016-0695-6.

Hippocampal sparing radiotherapy for glioblastoma patients: a planning study using volumetric modulated arc therapy

Jan Hofmaier  1 , Steffi Kantz  2 , Matthias Söhn  2 , Oliver S Dohm  3 , Stefan Bächle  3 , Markus Alber  4 , Katia Parodi  5 , Claus Belka  2 , Maximilian Niyazi  2
Affiliations

Hippocampal sparing radiotherapy for glioblastoma patients: a planning study using volumetric modulated arc therapy

Jan Hofmaier et al. Radiat Oncol. .

Abstract

Background: The purpose of this study is to investigate the potential to reduce exposure of the contralateral hippocampus in radiotherapy for glioblastoma using volumetric modulated arc therapy (VMAT).

Methods: Datasets of 27 patients who had received 3D conformal radiotherapy (3D-CRT) for glioblastoma with a prescribed dose of 60Gy in fractions of 2Gy were included in this planning study. VMAT plans were optimized with the aim to reduce the dose to the contralateral hippocampus as much as possible without compromising other parameters. Hippocampal dose and treatment parameters were compared to the 3D-CRT plans using the Wilcoxon signed-rank test. The influence of tumour location and PTV size on the hippocampal dose was investigated with the Mann-Whitney-U-test and Spearman's rank correlation coefficient.

Results: The median reduction of the contralateral hippocampus generalized equivalent uniform dose (gEUD) with VMAT was 36 % compared to the original 3D-CRT plans (p < 0.05). Other dose parameters were maintained or improved. The median V30Gy brain could be reduced by 17.9 % (p < 0.05). For VMAT, a parietal and a non-temporal tumour localisation as well as a larger PTV size were predictors for a higher hippocampal dose (p < 0.05).

Conclusions: Using VMAT, a substantial reduction of the radiotherapy dose to the contralateral hippocampus for patients with glioblastoma is feasible without compromising other treatment parameters. For larger PTV sizes, less sparing can be achieved. Whether this approach is able to preserve the neurocognitive status without compromising the oncological outcome needs to be investigated in the setting of prospective clinical trials.

Keywords: Glioblastoma; Hippocampal sparing; VMAT.

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Figures

Fig. 1
Fig. 1
Coronal view of the arc setup. a Two full coplanar arcs (horizontal line) and one arc from gantry angle 0 to 180° at couch angle 55° were sufficient in most cases (16 patients). b For the remaining 11 patients, an additional non-coplanar arc was introduced
Fig. 2
Fig. 2
Comparison of VMAT (a) and 3D-CRT (b) dose distributions for one patient. OARs are shown with their avoidance margins. Dose constraints for optic nerve (violet), chiasm (light brown, only the 3 mm expansion is visible in this slice) and the brain stem (green) prevent the 95 % isodose from completely covering the PTV (red). The reduced dose to the contralateral hippocampus (yellow) can be seen in the 30 % isodose line. The 5Gy isodose line shows that the dose to the lenses was limited to 5Gy
See this image and copyright information in PMC

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