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 < 0.01), reduced DSS (HR 5.84, P < 0.01), and an increased risk of ARE (HR 3.31, P = 0.04). Timing of SRS was correlated with reduced PFS for patients having early salvage treatment compared to upfront adjuvant (HR 3.17, P = 0.01) or late salvage treatment (HR 4.39, P < 0.01). 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.

Automated summary

This retrospective analysis of 68 patients with atypical meningiomas (AM) receiving stereotactic radiosurgery (SRS) showed poor progression-free survival (PFS) despite treatment. Prior external beam radiation therapy (EBRT) was associated with worse tumor control, higher tumor-related mortality, and an increased risk of adverse radiation events (AREs). Further research is needed to determine if upfront adjuvant SRS improves tumor control compared to salvage SRS.