The role of single-fraction stereotactic radiosurgery for atypical meningiomas (WHO grade II): treatment results based on a 25-year experience

Purpose To clarify the role of stereotactic radiosurgery (SRS) for atypical meningiomas (AM). Methods A retrospective analysis of 68 patients with AM having SRS from 1995 until 2019. Results Nineteen patients (28%) had undergone prior external beam radiation therapy (EBRT) (median dose, 54 Gy). The median follow-up period was 52 months. Eighteen (26%), 17 (25%), and 33 (49%) patients received SRS as an upfront adjuvant (≤ 6 months), early salvage (7-18 months), or late salvage treatment (> 18 months), respectively. The 3-, 5-, and 10-year progression-free survivals (PFSs) were 52%, 35%, and 25%, respectively. The 3-, 5-, and 10-year disease-specific survivals were 85%, 78%, and 61%, respectively. Adverse radiation events (AREs) were observed in 12 patients (18%), with increased or new seizures being the most frequent complication (n = 7). Prior EBRT was associated with reduced PFS (HR 5.92, P Conclusion PFS for patients with residual/recurrent AM remains poor despite SRS. Prior EBRT was associated with worse tumor control, higher tumor-related mortality, and an increased risk of ARE. Further study on the timing of SRS is needed to determine if upfront adjunctive SRS improves tumor control compared to salvage SRS.