Fractionated stereotactic radiation therapy in the management of primary optic nerve sheath meningiomas.

We analysed our long-term results after fractionated stereotactic radiotherapy (FSRT) in patients with primary optic nerve sheath (pONSM) meningioma, as a rare subtype of meningiomas. Between 01/1995 and 12/2007, 32 patients with pONSM were treated with FSRT. Fifteen patients received radiotherapy as primary treatment, four after biopsy, and six patients after surgical resection. Seven patients were irradiated for recurrent disease. Seventeen lesions were histologically proven and determined as WHO grade I pONSM. Median target volume was 15.7 cc, median total dose 54.9 Gy. Twenty-nine patients showed clinical symptoms before radiotherapy like reduced vision, unilateral loss of vision, or an exophthalmia. Median follow-up was 4.5 years. Overall local tumor control was 100%. Twenty-six patients had stable disease based on CT/MRI, while 6/32 had a partial remission of tumor volume. 97% of our patients showed stable vision or an improvement of visual acuity. Eleven patients (38%) showed an improvement of pre-existing clinical symptoms like double vision, exophthalmia and visual acuity. Only one patient showed an impairment of vision with progressive concentric decreasing of the visual field on the side of the irradiated ONSM. These data demonstrate that FSRT is an effective and safe treatment modality for local control in patients with pONSM with minimal risk of significant late toxicity.