Convexity Meningiomas in Patients with Neurofibromatosis Type 2: Long-Term Outcomes After Gamma Knife Radiosurgery

Background: Convexity meningiomas are common tumors requiring treatment in patients with neurofibromatosis type 2 (NF2). Although different therapeutic options are described for sporadic convexity meningioma, much less is known about these lesions in patients with NF2 despite their distinct biology and need for multiple treatments. We analyzed the value of Gamma Knife radiosurgery (GKRS) as definitive treatment for convexity meningiomas in patients with NF2. Methods: This international multicenter retrospective study was approved by the International Radiosurgery Research Foundation. Patients with NF2 with at least 1 convexity meningioma and 6-month follow-up after primary GKRS were included. Results: Inclusion criteria were met by 18 patients with NF2. A total of 120 convexity meningiomas (median treatment volume, 0.66 cm³ [range, 0.10–21.20 cm³]) were analyzed. Median follow-up after initial GKRS was 15.6 years (range, 0.6–25.5 years). Median age at GKRS was 32.5 years (range, 16–53 years). Median number of meningiomas per patient was 13 (range, 1–27), and median number of convexity lesions receiving GKRS per patient was 3.5 (range, 1–27). One case of tumor progression was reported 24 years after GKRS, leading to actuarial progression-free survival rates of 100% at 2, 5, and 10 years. No malignant transformation or death due to meningioma or radiosurgery was recorded. Conclusions: GKRS is safe and effective as definitive treatment of small to medium-sized convexity meningiomas in patients with NF2. Despite concerns about the particular mutational burden of these tumors, no malignant transformation manifested after treatment. GKRS represents a minimally invasive option that offers long-term tumor control to this specific group of patients.