Intensity-modulated fractionated stereotactic radiotherapy with reduced margin for high grade gliomas: dosimetric analysis of sparing optic nerve & chiasm.

The aim of this study was to evaluate the potential advantage of intensity modulation fractionated stereotactic radiotherapy (IM-FSRT) for sparing the optic nerve and chiasm in the management of anaplastic astrocytoma (AA) or glioblastoma (GBM). Clinical data of 16 patients with high grade gliomas were retrospectively reviewed. All patients had tumors close to the optic chiam that prohibited the full dose radiation therapy. The patients were treated with either IM-FSRT in conjunction with external beam radiation or IM-FSRT only to a total dose of 60 Gy. The final dosimetric analysis was performed. The estimated average maximum optic nerve and chiasm dose 48.6±5.0 Gy (range, 34.2-55.9). Conformity index reached as high as 0.98, and inhomogeneity coefficient was low enough to deliver the prescribed radiation dose. IM-FSRT showed excellent dose conformality to the target volume with superior normal tissue sparing effect. High precision therapy such as IM-FSRT could be a reliable treatment technique for the patients with AA or GBM for a maximal sparing of optic apparatus.