LAUSR

BACKGROUND: About one-third of anterior skull base meningiomas show Hedgehog pathway activation. We have recently identified GAB1 as a surrogate marker for Hedgehog pathway–activated meningiomas. OBJECTIVE: To determine the reproducibility and prognostic value of GAB1 marker in anterior skull base meningiomas. METHODS: A retrospective bicentric cohort of anterior skull base meningiomas, operated from 2005 to 2015, was constituted. GAB1 immunohistochemistry was performed in 2 centers, and the GAB1 score was assessed. Clinical and pathological data were reviewed to determine the prognostic value of the GAB1 score, along with classical factors of recurrence. RESULTS: One hundred forty-eight patients were included (median follow-up of 72 ± 46 months). 78% of patients had gross total resection. Eighty-four percentage of patients harbored grade 1 meningiomas. GAB1 immunohistochemistry was positive (ie, GAB1 staining score was >250) in 53 cases (35%). GAB1-positive cases were mainly at olfactory groove, of meningothelial grade 1 subtype, and showed greater recurrence (36% vs 14%, P = .002), greater requirement for multiple surgeries (17% vs 4.2%, P = .014), and more likely evolution toward diffuse skull base infiltration (15% vs 3%, P = .0017). By multivariable Cox regression analysis, incomplete surgical resection (hazard ratios [HR] = 8.3, 95% IC [3.7-18.2], P < .001), male sex (HR = 5.4, 95% IC [2.2-13.5], P < .001), GAB1 positivity (HR = 3.2, 95% CI [1.5-6.9], P = .004), and Ki67 index >4 (HR = 2.2, 95% IC [1.2-4.6], P = .035) were independent prognostic factors for recurrence. CONCLUSION: GAB1 marker is an independent prognostic factor for anterior skull base meningioma and could be useful for both prognostic evaluation and identification of Hedgehog-activated meningiomas.