Prognostic significance of brain invasion in meningiomas: systematic review and meta-analysis

Abstract

The WHO 2016 classification introduced brain invasion as a standalone criterion for grade II meningioma (GIIM). We systematically reviewed studies published after 2000 and performed a PRISMA-compliant meta-analysis of the hazard ratios (HRs) for progression-free survival (PFS) between brain-invasive and noninvasive meningiomas. In five studies that included both benign and higher-grade meningiomas, brain invasion was a significant risk factor for recurrence (HR\u2009=\u20092.45, p \u2009=\u20090.0004). However, in 3 studies comparing “brain-invasive meningioma with otherwise benign histology (BIOB)” with grade I meningioma, brain invasion was not a significant predictor of PFS (HR\u2009=\u20091.49, p \u2009=\u20090.23). Among GIIM per the WHO 2000 criteria, brain invasion was a significant predictor of shorter PFS than noninvasive GIIM (HR\u2009=\u20093.40, p \u2009=\u20090.001) but not per the WHO 2016 criteria (HR 1.13, p \u2009=\u20090.54), as the latter includes BIOB. Meta-regression analysis of seven studies of grade II meningioma showed that more frequent BIOB was associated with lower HRs ( p \u2009<\u20090.0001). Hence, there is no rationale for brain invasion as a standalone criterion for grade II meningioma, although almost all studies were retrospective and exhibited highly heterogeneous HRs due to differences in brain–tumor interface data availability.