Objective: The optimal management of neurofibromatosis type 2 (NF2)-associated meningiomas must be personalized case by case. Stereotactic radiosurgery (SRS) is one option for patients with one or multiple intracranial meningiomas associated with the NF2 mutation. In this study, the authors evaluated their single-institution experience of SRS treatment for NF2-associated meningiomas.
Methods: The medical records and radiographic images of 45 patients (20 males, 213 tumors) with a median age of 53.5 (range 20-79) years who underwent SRS between 1987 and 2022 were retrospectively reviewed. The median Karnofsky Performance Status score was 80 (range 50-100). Twenty-seven patients had undergone prior resection, and 8 had undergone prior fractionated radiation therapy. The median Ki-67 proliferation index (n = 8) was 11.5% (range 9%-27.5%). The median margin dose was 13 (range 9-16) Gy. The median number of meningiomas per patient was 3 (range 1-17), and the median cumulative tumor volume treated per patient was 6.29 (range 0.10-37.70) cm3.
Results: The 5-, 10-, and 15-year local tumor control (LTC) rates per tumor were 90.21%, 84.46%, and 84.46%, respectively. On multivariate analysis, a lower tumor volume was associated with better LTC (p = 0.02; HR 1.07, 95% CI 1.01-1.12). After the initial SRS, 20 (44%) patients developed a previously untreated meningioma. Patients with more meningiomas at the time of SRS had a higher rate of new meningioma development (p = 0.01; HR 1.19, 95% CI 1.04-1.37). Eighteen patients died during the follow-up interval, of which 5 deaths were related to the progression of one or more intracranial NF2-related tumors. Two (4.44%) patients developed transient adverse radiation effects. No patient developed a secondary malignancy. Eight patients required additional SRS for local tumor progression, 20 underwent SRS for new tumor development, and 4 patients underwent delayed resection of an SRS-treated meningioma.
Conclusions: In this case series, the LTC rates of both primary and salvage SRS exceeded 90%. However, nearly half of the patients required additional SRS for new untreated meningiomas. No significant differences in long-term LTC were found when comparing upfront versus salvage SRS for patients with NF2 meningiomas. These results establish SRS as a valuable and safe option for managing NF2-associated meningiomas.
Keywords: Gamma Knife; meningiomas; neurofibromatosis type 2; stereotactic radiosurgery.