Preliminary visual outcomes after three-dimensional conformal radiation therapy for optic nerve sheath meningioma

Abstract

Purpose We assessed visual outcomes, local control, and toxicity associated with three-dimensional conformal radiation therapy (3D-CRT) for primary optic nerve sheath meningiomas (ONSM). Methods Twenty-three patients diagnosed with ONSM were evaluated at the University of Michigan between 1986 and 2001. Fourteen patients were treated with 3D-CRT. Detailed pre- and postradiation treatment ophthalmologic examinations and MRIs were performed on all patients. Clinically significant visual acuity change was defined as a ≥three line change on the Snellen chart. Mean deviation change of ≥three decibels was defined as a clinically significant visual field change. Radiographic progression was defined as any increase in size on MRI. Acute and late toxicity was scored according to RTOG criteria. Results Median follow-up was 51.3 months. Five patients had a clinically significant improvement in visual acuity. Seven had stable acuity, and only 2 worsened. Nine patients had clinically significant visual field improvement. One patient developed early radiation retinopathy, 1 experienced orbital pain, 1 developed dry eye, and 2 developed iritis. No patient has required additional treatment, and none have demonstrated radiographic progression. Conclusions 3D-CRT is effective in controlling tumor growth while improving or preserving vision in most patients with optic nerve sheath meningiomas.