Predictors of recurrence and postoperative outcomes in patients with non-skull base meningiomas based on modern neurosurgical standards

Background: Advances in neurosurgical techniques and neuroimaging resolution questions the modern-day reliability of the Simpson grade for predicting meningioma recurrence. Therefore, we evaluated the reliability of predictors for recurrence and outcomes in detail in patients with non-skull base meningiomas (NSBMs). Methods: We retrospectively analyzed data from consecutive 175 NSBMs underwent surgical resection. We performed Kaplan–Meier analyses of recurrence-free survival (RFS) according to Simpson and World Health Organization (WHO) grades. Predictors of RFS and clinical deterioration were estimated by univariate and multivariate analyses. Correlation between the Simpson grade and change in Karnofsky Performance Scale scores was assessed by Fisher's exact test. Results: Log-rank tests revealed significant correlations of both the Simpson and WHO grades with RFS for the overall cohort, convexity, and falx/tentorium meningioma. Unlike patients undergoing Simpson grade I and II resections, RFS in patients with WHO grade I and II/III tumors differed significantly from the early postoperative stage. Multivariate analysis identified tumor size, Simpson grade, and MIB-1 labeling index as significant predictors of RFS. Clinical deterioration was more frequent among patients undergoing less aggressive resection. Tumor location was the only significant predictor of clinical deterioration. Conclusions: Our findings indicate that tumor size, Simpson and WHO grades, and MIB-1 labeling index are significant predictors of NSBM recurrence. Moreover, the risk of recurrence markedly decreases within the follow-up duration of 80 months. Aggressive resection appears to minimize the risk of recurrence without evidence of clinical deterioration. Follow-up schedules should be based on the WHO grade and extent of resection. Keywords: Meningioma, Non-skull base, Outcome, Recurrence, Simpson grade, WHO grad