PURPOSE: This study assesses a large multi-institutional database to present the outcomes of World Health Organization grade 2 meningiomas treated with stereotactic radiosurgery (SRS). We also compare the 3-year progression-free survival (PFS) to that reported in the Radiation Therapy Oncology Group 0539 phase 2 cooperative group meningioma trial. METHODS AND MATERIALS: From an international, multicenter group, data were collected for grade 2 meningioma patients treated with SRS for demonstrable tumor from 1994 to 2019. Statistical methods used included the Kaplan-Meier method, Cox proportional hazards analysis, and recursive partitioning analysis. RESULTS: Two hundred thirty-three patients treated at 12 institutions were included. Patients presented at a median age of 60 years (range, 13-90), and many had at least 2 prior resections (30%) or radiation therapy (22%). Forty-eight percent of patients had prior gross total resection. At SRS, the median treatment volume was 6.1 cm3 (0.1-97.6). A median 15 Gy (10-30) was delivered to a median percent isodose of 50 (30-80), most commonly in 1 fraction (95%). A model was developed using recursive partitioning analysis, with one point attributed to age >50 years, treatment volume >11.5 cm3, and prior radiation therapy or multiple surgeries. The good-prognostic group (score, 0-1) had improved PFS (P < .005) and time to local failure (P < .005) relative to the poor-prognostic group (score, 2-3). Age >50 years (hazard ratio = 1.85 [95% confidence interval, 1.09-3.14]) and multiple prior surgeries (hazard ratio = 1.80 [1.09-2.99]) also portended reduced PFS in patients without prior radiation therapy. Two hundred eighteen of 233 patients in this study qualified for the high-risk group of Radiation Therapy Oncology Group 0539, and they demonstrated similar outcomes (3-year PFS: 53.9% vs 58.8%). The good-prognostic group of SRS patients demonstrated slightly improved outcomes (3-year PFS: 63.1% vs 58.8%). CONCLUSIONS: SRS should be considered in carefully selected patients with atypical meningiomas. We suggest the use of our good-prognostic group to optimize patient selection, and we strongly encourage the initiation of a clinical trial to prospectively validate these outcomes.

Center of Image Guided Neurosurgery University of Pittsburgh Medical Center Pittsburgh Pennsylvania

Centro Gamma Knife Dominicano CEDIMAT Plaza de la Salud Santo Domingo Dominican Republic

Department of Medical Physics NYU Langone Health System New York New York

Department of Neurologic Surgery Cleveland Clinic Foundation Cleveland Ohio

Department of Neurologic Surgery Mayfield Clinic Cincinnati Ohio

Department of Neurologic Surgery University of Southern California Los Angeles California

Department of Neurologic Surgery University of Virginia Health System Charlottesville Virginia

Department of Neurologic Surgery West Virginia University Morgantown West Virginia

Department of Neurosurgery NYU Langone Health System New York New York

Department of Neurosurgery Université de Sherbrooke Centre de recherche du CHUS Sherbrooke Québec Canada

Department of Radiation Oncology Beaumont Health Royal Oak Michigan

Department of Radiation Oncology Mayo Clinic Rochester Minnesota

Department of Radiation Oncology University of Southern California Los Angeles California

Department of Radiology Taipei Veteran General Hospital Taipei Taiwan; National Yang Ming University School of Medicine Taipei Taiwan

Department of Stereotactic and Radiation Neurosurgery Na Homolce Hospital Prague Czech Republic

Mayo Clinic Department of Radiation Oncology Mayo Clinic Jacksonville Florida

National Yang Ming University School of Medicine Taipei Taiwan; Department of Neurosurgery Taipei Veteran General Hospital Taipei Taiwan

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