Salvage Stereotactic Radiosurgery for Recurrent WHO Grade 2 and 3 Meningiomas: A Multicenter Study (STORM)

Purpose: The role of stereotactic radiosurgery (SRS) in the management of grade 2 and 3 meningiomas is not well elucidated. Unfortunately, local recurrence rates are high, and guidelines for management of recurrent disease are lacking. To address this knowledge gap, we conducted STORM (Salvage Stereotactic Radiosurgery for Recurrent WHO Grade 2 and 3 Meningiomas), a multicenter retrospective cohort study of patients treated with primary SRS for recurrent grade 2 and 3 meningiomas.

Methods and materials: Data on patients with recurrent grade 2 and 3 meningioma treated with SRS at first recurrence were retrospectively collected from 8 academic centers in the United States. Patients with multiple lesions at the time of initial diagnosis or more than 2 lesions at the time of first recurrence were excluded from this analysis. Patient demographics and treatment parameters were extracted at time of diagnosis, first recurrence, and second recurrence. Oncologic outcomes, including progression-free survival (PFS) and overall survival, as well as toxicity outcomes, were reported at the patient level.

Results: From 2000 to 2022, 108 patients were identified (94% grade 2, 6.0% grade 3). A total of 106 patients (98%) had upfront surgical resection (60% gross-total resection) with 18% receiving adjuvant radiation therapy (RT). Median time to first progression was 2.5 years (IQR, 1.34-4.30). At first recurrence, patients were treated with single or fractionated SRS to a median marginal dose of 16 Gy to a maximum of 2 lesions (87% received single-fraction SRS). The median follow-up time after SRS was 2.6 years. The 1-, 2-, and 3-year PFS was 90%, 75%, and 57%, respectively, after treatment with SRS. The 1-, 2-, and 3-year overall survival was 97%, 94%, and 92%, respectively. In the multivariable analysis, grade 3 disease (HR, 6.80; 95% CI, 1.61-28.6), male gender (HR, 3.48; 95% CI, 1.47-8.26), and receipt of prior RT (HR, 2.69; 95% CI, 1.23-5.86) were associated with worse PFS. SRS dose and tumor volume were not correlated with progression. Treatment was well tolerated, with a 3.0% incidence of grade 2+ radiation necrosis.

Conclusions: This is the largest multicenter study to evaluate salvage SRS in recurrent grade 2 and 3 meningiomas. In this select cohort of patients with primarily grade 2 meningioma with a potentially more favorable natural history of delayed, localized first recurrence amenable to salvage SRS, local control rates and toxicity profiles were favorable, warranting further prospective validation.