Long-term response to fractionated radiotherapy of presumed optic nerve sheath meningioma.

BACKGROUND/AIMS To review the long-term results of treatment of optic nerve sheath meningiomas (ONSMs) with conformal radiotherapy. METHODS Eleven patients with presumed ONSM were treated with fractionated conformal radiotherapy using 45-54 Gy in 25-30 fractions and followed for more than 5 years. Affected eye visual acuity in logMAR notation, colour vision, threshold perimetry, mean deviation (dB) and imaging were studied before and after treatment. ANALYSIS Included adverse effects of treatment and the frequency of affected eye maintained or improved vision. RESULTS There were nine women and two men with a mean age of 45.3. Vision or field loss was the most common presentation. All had abnormal MR imaging. The follow-up period after radiotherapy was 61-156 months (mean 89.6). Visual acuity was unchanged or improved in 10 patients (91%). The average difference between pretreatment and final logMAR visual acuity was 0.08, while the average difference in visual-field mean deviation was -4.63 dB. The radiographic appearance of the tumours was stable in size in nine patients and decreased in two. No major side effects from radiation were seen. CONCLUSIONS Vision, MRI and complication outcomes are favourable for using fractionated conformal radiotherapy for ONSM.