The management of WHO Grade II "atypical" meningiomas (AMs) and Grade III "malignant" meningiomas (MMs) remains controversial and under-investigated in prospective studies. The roles of surgery, radiation therapy, radiosurgery, and chemotherapy have been incompletely delineated. This has left physicians to decipher how they should treat patients on a case-by-case basis. In this study, the authors review the English-language literature on the management and clinical outcomes associated with AMs and MMs diagnosed using the WHO 2000/2007 grading criteria. Twenty-two studies for AMs and 7 studies for MMs were examined in detail. The authors examined clinical decision points using the literature and concepts from evidence-based medicine. Acknowledging the retrospective nature of the studies concerning AM and MM, the authors did find evidence for the following clinical strategies: 1) maximal safe resection of AM and MM; 2) active surveillance after gross-total resection of AM; 3) adjuvant radiation therapy after subtotal resection of AM, especially in the absence of putative radioresistant features; and 4) adjuvant radiation therapy after resection of MM.
Keywords: AM = Grade II meningioma (atypical meningioma); EBM = evidence-based medicine; EBRT = external beam radiation therapy; EGFR = epidermal growth factor receptor; EOR = extent of resection; GTR = gross-total resection; LC = local control; MM = Grade III meningioma (malignant meningioma); NTR = near-total resection; OS = overall survival; PDGFR = platelet-derived growth factor receptor; PFS = progression-free survival; RTK = receptor tyrosine kinase; SRS = stereotactic radiosurgery; STR = subtotal resection; VGFR = vascular endothelial growth factor receptor; anaplastic meningioma; atypical meningioma; malignant meningioma; meningioma.