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.