Multi-Institutional Study of Stereotactic Radiosurgery for Recurrent WHO Grade 2/3 Meningiomas: An Interim Analysis

Abstract

Meningiomas are the most common tumors of the central nervous system (CNS). Approximately 80% are classified as World Health Organization (WHO) grade 1, while 20% correspond to grade 2 or grade 3. In those with grade 2/3 disease, local recurrence is not uncommon. Salvage treatment options vary widely and include resection, external beam radiation therapy (EBRT), stereotactic radiosurgery (SRS), and/or clinical trials. Although retrospective studies have reported on the use of upfront SRS in grade 2/3 meningiomas, large-scale outcomes with SRS in the recurrent setting are lacking. The objective of this study was to report on oncologic outcomes for patients with recurrent grade 2/3 meningioma treated with SRS. This is an ongoing multi-institutional retrospective cohort study. Eligibility criteria include patients >18 years old with pathologically confirmed WHO grade 2 or 3 meningioma treated with SRS monotherapy at the time of first recurrence. Patients require pathologic confirmation only at time of diagnosis; those with upfront grade 1 disease must have pathologic confirmation of grade 2/3 disease at time of first recurrence. Patients with multifocal disease upfront were excluded from this study. A total of 60 patients met eligibility criteria. Baseline demographics at time of initial diagnosis are shown in table 1. At the time of first recurrence, 57 (95%) were WHO grade 2, and 3 (5%) were grade 3. Median follow up time from first recurrence was 5.02 years. Median marginal SRS dose was 16 Gy (IQR 14-17) to a 2.67cc planning treatment volume (IQR 1.4-5.1). 92% of patients received single fraction SRS. Median time to second recurrence was 5.92 years. 1, 3, and 5-year progression-free survival (PFS) was 95%, 68%, and 51%, respectively. 1, 3, and 5-year overall survival (OS) was 100%, 98%, and 96%, respectively. On multivariate analysis, grade 3 disease was independently associated with worse PFS (HR 15.7, p = 0.03). Median SRS dose and treatment volume did not correlate with PFS. 1 patient (1.7%) experienced symptomatic radiation necrosis requiring steroids, 3 (5.0%) experienced new seizure activity, and 2 (3.3%) additional patients showed clinical evidence of post-treatment neurocognitive decline. Based on this interim analysis, primary SRS for recurrent grade 2/3 meningioma appears safe and feasible, with outcomes comparable to prospective data on high-risk grade 2/3 patients treated with post-operative fractionated EBRT. We look forward to further analysis with a larger cohort which may help guide further prospective studies.