Differentiating Meningioma Grade by Imaging Features on MRI

Background: Atypical meningiomas have a more aggressive clinical course. Distinguishing typical from atypical meningiomas could affect surgical planning and improve treatment outcomes for patients. To date, no single pre-operative imaging feature has been shown as predictive of higher-grade meningioma. In this study, we examined whether magnetic resonance imaging (MRI) features could distinguish between benign and atypical meningiomas. These data provide cogent evidence for evaluating pre-operative radiographic features and their role in surgical decision making for patients with meningiomas.

Methods: MRI imaging from 128 patients with benign and atypical meningiomas was retrospectively evaluated and correlated with histological grade to determine whether imaging features were predictive of more aggressive meningiomas. Post-operatively, it was determined that 94 tumors were WHO Grade I and 34 tumors were WHO Grade II. All meningiomas were histologically graded after surgical resection by a neuro-pathologist according to the WHO guidelines. Two board-certified neuroradiologists, who were blinded to clinical history and pathologic grade, reviewed the pre-operative T2-weighted and post-contrast, T1-weighted sequences. Imaging factors analyzed included severity of peritumoral edema, the presence of a draining vein, tumor necrosis, tumor location and tumor volume. Univariate and multivariate logistic regression models were used and statistical significance was set a priori at p < 0.05.

Results: Imaging features associated with increased risk for atypical meningioma in univariate analysis included the presence of tumor necrosis by imaging (p = 0.012), increased peritumoral edema (p = 0.022), and location along the falx and convexity (p = 0.026). Notably, increased tumor volume was the single-most predictive feature of higher grade meningioma (p < .001). Presence of a draining vein (p = 0.079) and male sex (p = 0.072) trended toward significance, and patient age at diagnosis (p = 0.76) and race (p = 0.47) were not predictive of higher grade meningioma. Despite statistically significant associations using univariate analysis, we found that only peritumoral edema was predictive of a higher-grade meningioma (p = 0.037) using a multivariate regression model. Interestingly, edema, draining vein and necrosis are all positive predictors of tumor volume (p < 0.0001). However, when adjusted for volume, edema is not predictive of higher grade meningioma (p = 0.204). Conversely, independent of peritumoral edema, volume is a robust predictor of higher-grade meningioma (p = 0.042).

Conclusion: These data suggest that radiographic features including presence of tumor necrosis, location along the falx or convexity and increased peritumoral edema are predictive of higher-grade meningioma when considered alone. However, when a multivariate regression model was used, only edema was predictive of higher-grade meningioma. Strikingly, increased tumor volume was the strongest predictor of higher-grade meningioma. Severity of peritumoral edema was not predictive of higher-grade meningioma when controlled for volume. However, volume remained the strongest predictor of higher-grade meningioma. Edema, presence of draining vein, and necrosis were also associated with increased tumor volume in multivariate analysis. Taken together, these data suggest that tumor volume is the strongest single predictor of higher-grade meningioma. Contributions of peritumoral edema, necrosis, draining vein and location of tumor can also be taken into account. These data provide the first description of radiographic predictors of higher-grade meningiomas and identify a myriad of imaging variables to consider when building a surgical treatment plan.