Safety, efficacy and feasibility of hypofractionated gamma knife radiosurgery for perioptic meningiomas: results from a large series

Background - Perioptic meningiomas are benign tumors arising in the proximity of the optic pathways. Despite showing non-aggressive features histologically in the majority of cases, they can grow to be a significant burden for patients’ quality of life, causing visual deterioration or other neurological deficits or symptoms. Surgical resection has historically been considered the mainstay for the treatment of these tumors but is often associated with non-negligible morbidity and mortality. Radiosurgery with Gamma Knife (GKRS) has progressively emerged as an effective alternative to surgery in some cases and nowadays is preferred when a patient may present contraindications to surgery. Hypofractionation of the treatment may reduce the toxicity to the optic pathways. Materials & Methods - We retrospectively reviewed our registries for patients treated with GKRS for perioptic meningiomas with hypofractionated scheme (three fractions in three consecutive days) from January 2007 to August 2023 (with at least 24 months follow-up). We identified 231 patients: 46 were lost to follow-up so our population comprised 185 patients harboring 190 meningiomas. Female patients were 139, accounting for 75.1% of the total and mean age of the population at the time of treatment was 56.7 years (median 56 years), with a SD of 12.6 years. One hundred-thirty-two tumors (69.5%) received fractionated GKRS (fGKRS) as primary treatment. At the time of treatment, mean target tumor volume was 7.2 cm3. For 89 lesions (46.8%), varying degrees of visual symptoms were present before the treatment. Mean clinical follow-up was 55.8 months and mean radiological follow-up was 46.7 months. Results - At last clinical follow-up, 6 patients had died (none of those died due to the meningioma). Mean overall survival (OS) was 123.6 months. Three- , 5- and 8-years OS was 98.8%, 96.5% and 94.1%, respectively. At last MRI, 95.8% of tumors appeared stable or reduced in size. At volumetric analysis (possible for 119 lesions which represented 62.6% of total tumors), a mean reduction of 18% of total volume was observed after treatment. Six lesions out of a total of 190 (3.2%) needed further treatments after radiosurgical treatment, so at last follow-up overall clinical tumor control (CTC) was 96.8%. Patients presenting visual deterioration after treatment were 12.1% of the total. Conclusions - Fractionated GKRS represents in our experience an effective treatment for perioptic meningiomas with limited morbidity.