INTRODUCTION. The concern about radiation induced optic neuropathy (RION) strongly characterized the recent past. This has probably been the main limit to a wider diffusion of radiotherapy and radiosurgery as treatment of meningiomas involving the anterior optic pathways. In spite of this consideration, during the last few years the radiotherapy activity for such lesions is continuously increasing. The aim of the present study is to define the risk of RION on a medium to long term follow-up period in a large series of patients treated by radiosurgery. The efficacy of the treatment is also investigated. MATERIALS AND METHODS: The visual outcome of 97 patients which underwent radiosurgery due to a meningioma involving the anterior optic pathways has been retrospectively evaluated. Patients with a minimum follow-up period longer than 12 months were included. Sixteen patients had a single session radiosurgery (sSRS) with a mean dose of 12 Gy (range 8-13 Gy; median 13 Gy). In these cases the mean tumour volume was 4,9 cc (range 0,3-10,5 cc; median 3.6 cc) Eighty-one patients underwent a multi-session radiosurgery (mSRS). The mean prescription dose was 24 Gy (range 15-30Gy; median 25Gy), the mean tumour volume was 9,5 cc (range 0,5-65 cc; median 6,5 cc) The visual outcome was evaluated in all cases. All the included patients had at least a pre-treatment and a last follow-up visual function assessment. Furthermore local control has been analyzed. RESULTS: The mean follow-up is 43 months (range 12-96 months; 56 patients f-up ≥ 36 monts; 23 patients f-up ≥ 60 months) Compared to the baseline the visual function improved in 24 patients (24 %) and was unchanged in 65 (68 %). Seven patients worsened 8 (8 %). Three out of these experienced a tumour progression. Only two patients with no progression disease developed a “de novo” visual deficit. At the analysis time, the overall local control was 94 %. Eighteen lesions (18%) showed a partial shrinkage, seventy-three (72%) were stable and 6 patients (6%) experienced a progression of the disease. When observed, the tumour progression always occurred later than 36 months post-treatment. CONCLUSIONS: The study confirms the low risk of radiation induced optic neuropathy both in case of sSRS and mSRS. Multisession radiosurgery makes also the larger lesions manageable. The high local control rate and the low toxicity suggest that radiosurgery could be proposed also as a primary treatment.
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