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S246: EXTENT OF RESECTION, KI-67, AND ADJUVANT RADIOTHERAPY PREDICT RECURRENCE AND SURVIVAL IN HIGH-GRADE MENINGIOMAS: A RETROSPECTIVE STUDY OF WHO GRADE II/III TUMORS AT A SINGLE INSTITUTION
Anthony Y Chen, BA; Aneesh P Reddy, BS; Toren Ikea-Mario, BS; Shray Jain, BS, MS; Zhenghao Xiao, MS; Nilanjan Haldar, MD; Rui Feng, MD, MS; James J Evans, MD; Wenyin Shi, MD, PhD; Thomas Jefferson University

INTRODUCTION: High-grade meningiomas (WHO Grade II/III) are associated with high recurrence rates and poor survival despite aggressive therapy. While adjuvant radiotherapy (RT) is standard after subtotal resection (STR), its benefit after gross total resection (GTR) remains uncertain. Histopathologic markers such as Ki-67 may further refine risk stratification and inform postoperative management. This study aimed to identify clinicopathologic predictors of local failure-free survival (LFFS) and overall survival (OS) in high-grade meningiomas, and to describe outcomes by extent of resection, receipt of adjuvant RT, proliferative index, and preoperative tumor volume.

METHODS: We retrospectively reviewed 82 patients with newly diagnosed high-grade meningiomas (70 Grade II, 12 Grade III) treated between 2005 and 2024 at our single institution. Demographic, surgical, RT, and histopathologic variables were collected. Preoperative tumor volumes were quantified using autosegmentation across four MRI sequences with the Cancer Imaging Phenomics Toolkit (CaPTk) and validated by a radiation oncologist. Continuous variables were dichotomized using thresholds established in literature (e.g., Ki-67 ≥13%). LFFS and OS were estimated using Kaplan–Meier analysis and compared by log-rank test. Variables with p<0.05 on univariable analysis and those deemed clinically relevant were entered into multivariable Cox models to identify independent predictors of LFFS and OS. Exploratory subgroup analyses were performed to compare outcomes between four treatment groups defined by extent of resection (GTR vs STR) and receipt of adjuvant RT. 

RESULTS: Median follow-up was 30.3 months (range 0.5–364.2). Local failure occurred in 40 patients (48.1%) and mortality in 22 (26.8%). Two- and three-year LFFS were 64.7% and 58.9%, respectively, while two- and three-year OS were 79.9% and 77.9%. On multivariable analysis, Ki-67 ≥13% independently predicted shorter LFFS (HR 5.50, 95% CI 1.38–21.94, p=0.016), and STR alone independently predicted worse OS (HR 3.98, 95% CI 1.19–13.33, p=0.025). Grade III tumors had higher Ki-67 (median 38% vs 13%, p=0.0002) and significantly worse LFFS (median 12.3 vs 83.5 months, p<0.0001) and OS (median 45.8 vs 364.2 months, p<0.0001) compared with Grade II tumors. In exploratory subgroup analysis, adjuvant RT significantly improved LFFS and OS after STR (p=0.0005 and p=0.0001, respectively) and was also associated with improved outcomes after GTR (p=0.0214 for LFFS and p=0.0116 for OS). STR alone had the poorest 2-year OS (17.9%), whereas GTR+RT had the highest (95.0%). Preoperative tumor volume was not significantly associated with LFFS or OS on univariable or multivariable Cox regression.

CONCLUSION: High-grade meningiomas carry high risks of recurrence and mortality. Ki-67 ≥13%, STR, and Grade III histology predicted poor outcomes, while adjuvant radiotherapy significantly improved local control and survival after both STR and GTR. Although not independently prognostic, our incorporation of an autosegmentation-based volumetric analysis represents a novel approach to quantifying tumor burden in high-grade meningiomas. These findings support not only maximal safe resection but also underscore the importance of postoperative radiotherapy guided by proliferation index and tumor grade.

 

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