2025 Proffered Presentations
S192: MENINGIOMAS CLASSIFIED AS GRADE 2 DUE TO BRAIN INVASION ALONE HAVE BETTER PROGRESSION-FREE SURVIVAL THAN OTHER GRADE 2 MENINGIOMAS
Georgios A Maragkos, MD; Georgios Mantziaris, MD; Carson Brantley, MS; Salem Tos, MBBS; Maria-Beatriz Lopes, MD; Ashok R Asthagiri, MD; University of Virginia
Background: Grade 2 meningiomas are associated with higher recurrence rates than Grade 1 and are subject to different treatment algorithms. In 2016, brain invasion (BI) was added as a major Grade 2 criterion to the World Health Organization (WHO) guidelines. Thus, meningiomas with BI and no other atypical features (BI-only) are now classified as Grade 2. However, large meningiomas being compressed against the underlying cortical surface are liable to eventually penetrate the pia mater and exhibit BI, regardless of their genotypic makeup and, possibly, their recurrence potential.
Objective: In this work we aim to investigate whether BI-only meningiomas have longer time-to-recurrence than other Grade 2 meningiomas.
Methods: A single-institutional retrospective cohort study was conducted between 2003-2023. Patients with meningiomas resected during the study period were identified, their pathology reports were reviewed and re-graded based on the current WHO criteria (including BI). WHO Grade 2 patients were included in the study. Exclusion criteria were: spinal meningiomas, prior treatment, follow-up <3 months. Patients were classified into two cohorts: "BI-only", if they were deemed Grade 2 due to BI alone and were negative for other criteria; and "other criteria" (OC), if Grade 2 criteria other than BI were present. The primary outcome was time-to-recurrence (TTR). Associations of each of the collected variables with time-to-recurrence (TTR) were explored using univariate Cox regressions. Multivariable Cox regression was conducted to investigate the association of BI-only status with TTR, controlling for gross total resection (GTR) status, and posterior fossa location.
Results: A total of 131 patients were included. Mean (SD) age was 59.2±15.9 years, and 79 (60%) patients were female. Median [IQR] preoperative tumor volume was 34cc [16-59]. There were 97 (74%) convexity meningiomas, 29 (22%) skull base, and 5 (4%) posterior fossa. GTR, defined as Simpson grade 1-2, was achieved in 69 (53%) tumors. Eighteen patients (14%) had adjuvant radiation. BI was noted in 78 (60%) patients, with 45 (34%) being classified as Grade 2 based on BI alone (BI-only group). High mitotic count was present in 60 (46%) patients, and minor criteria in 38 (29%). Mean radiographic follow-up was 74±56 months. Recurrence was noted in 40 (31%) patients, a mean 40±39 months post-resection. Of the 45 BI-only patients, recurrence was noted in 8 (18%). On univariate Cox regression, TTR was associated with being in the BI-only group (Hazard Ratio HR=0.44, P=0.036), GTR (HR=0.29, P<0.001), and residual volume (HR=1.04, P=0.002). On multivariable Cox regression, the BI-only group was associated with longer TTR (HR=0.44, P=0.041), when controlling for GTR and posterior fossa location. This association was robust through sensitivity analyses 1) excluding OC patients who also had BI, 2) transferring patients with small tumors (lowest preoperative volume quartile) from the BI-only to the OC group.
Conclusions: Meningiomas classified as Grade 2 due to brain invasion alone were associated with significantly longer TTR than tumors with other Grade 2 criteria. This was especially robust for larger BI-only tumors. Further research is necessary to delineate if brain invasion should truly be a standalone criterion for Grade 2 classification.
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