Extent of Resection Predicts Recurrence-Free Survival in Who Grade II-III Meningiomas: A Population-Based Cohort Study

Background: Atypical (WHO II) and anaplastic (WHO III) meningiomas demonstrate higher recurrence rates than benign meningiomas, but the relative impact of surgical extent of resection (EOR) and adjuvant radiotherapy (RT) on recurrence-free survival (RFS) remains uncertain. Clarifying prognostic factors is essential to guide surgical decision-making and optimize adjuvant treatment strategies. Methods: We performed a retrospective, population-based cohort study of adult patients who underwent resection of WHO grade II–III meningiomas in Saskatchewan between 2007–2017. Demographic, clinical, radiographic, and pathologic features were collected. Simpson grade was grouped into gross total resection (GTR, 1–3) versus subtotal resection (STR, 4–5). Kaplan–Meier methods estimated RFS, and Cox proportional hazards models adjusted for age, sex, WHO grade, RT, skull base, tumour location, brain invasion and tumor necrosis. Interaction terms assessed modification by RT. Results: Eighty-six patients were analyzed, including 81 GTR and 5 STR. The mean age was 59 years; 54% were female. STR patients more often harbored skull base tumors (60% vs 15%, p = 0.035). Overall, 25 recurrences occurred. Five-year RFS was 70% (95% CI 61–81) for GTR versus 60% (29–100) for STR. By WHO grade, 5-year RFS was 70% (60–81) for grade II and 67% (42–100) for grade III. Patients not receiving RT demonstrated higher 5-year RFS (74%, 64–85) than those receiving RT (51%, 31–86), consistent with selection of higher-risk cases for adjuvant therapy. On multivariable analysis, STR independently predicted recurrence (HR 12.7, 95% CI 1.10–146.1, p = 0.041). Tumor necrosis was also significantly associated with recurrence (HR 3.17, 95% CI 1.09–9.22, p = 0.03). Adjuvant RT was associated with increased recurrence risk (HR 3.23, 95% CI 1.03–10.1, p = 0.04), though interpretation is limited by confounding by indication. WHO grade was not a significant predictor of RFS (p = 0.99). No significant interaction was observed between RT and EOR or WHO grade. Conclusion: In this population-based cohort, extent of resection and tumor necrosis emerged as the strongest predictors of recurrence in WHO grade II–III meningiomas. WHO grade was not associated with recurrence-free survival. Adjuvant RT was linked to inferior outcomes, likely reflecting underlying patient selection rather than true therapeutic effect. These findings highlight the importance of maximizing safe resection as the cornerstone of surgical management for high-grade meningiomas, while underscoring the need for improved risk stratification to guide postoperative RT. Publication History Article published online: 27 February 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany