Clinical investigation: brain
Preliminary visual outcomes after three-dimensional conformal radiation therapy for optic nerve sheath meningioma

Presented at the 44th Annual Meeting of the American Society of Therapeutic Radiation and Oncology in New Orleans, Louisiana, October 2002.
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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.

Introduction

Primary optic nerve sheath meningiomas (ONSM) arise from the meninges of the optic nerve, and account for 1%–2% of all meningiomas. Although ONSM is considered benign and occurs infrequently, it is nevertheless an important clinical entity because of its ability to cause unilateral or, if untreated, bilateral blindness.

In the past, patients often presented late in the course of disease with advanced visual decline. Increased awareness and improved imaging modalities allow earlier detection. However, consensus regarding how these patients should be managed does not exist, and treatment options for ONSM vary widely, ranging from observation to radiation therapy to surgery 1, 2, 3, 4. In particular, the management of patients with normal visual function or early progressive visual loss is contentious. In the absence of data demonstrating the efficacy of radiation therapy early in the course of disease, some advise observation followed by delayed radiation therapy or surgery (5). Others have reported cases of stabilization or improvement of vision with low rates of complications after treatment with radiation therapy 6, 7, 8, 9, 10. We performed a review of patients with ONSM from our institution to assess visual outcomes following treatment with three-dimensional conformal radiation (3D-CRT) therapy.

Section snippets

Patient selection

We sought to identify all patients with presumed or pathologically proven primary optic nerve sheath meningiomas who were evaluated at the Kellogg Eye Center at the University of Michigan between 1986 and 2001. Searches of patient databases at the Kellogg Eye Center identified 23 such patients. Patients with meningiomas of the sphenoid wing or planum sphenoidale with secondary involvement of the optic nerve were excluded. Of these 23 patients, 14 underwent 3D-CRT and comprise the primary

Visual response

Five patients experienced clinically significant improvements in visual acuity (i.e., more than three-line improvement on the Snellen chart). A patient with 20/100 acuity initially improved to 20/25 and had full recovery of color discrimination and improved contrast sensitivity. Two other patients with 20/50 initially improved to 20/20 and 20/25. Two patients who were only able to count fingers initially had improved acuity to 20/70 and 20/200. Seven patients had stable visual acuity after

Discussion

Management of primary ONSM has remained controversial and includes observation, radiation therapy, or surgery. The natural history of this disease is progressive loss of visual acuity, as evidenced by a cohort of patients who underwent observation in Kennerdell’s series (2). Of 9 patients with minimal visual loss (20/40 or better) who were observed, all had worsening vision within 5 years, requiring eventual treatment. Furthermore, 6 of 7 patients from our institution undergoing observation

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