MIB-1 index predicts low recurrence risk after subtotal resection of meningiomas: a retrospective study of 505 patients.

The Ki-67/MIB-1 index, a biomarker of cellular proliferation, holds prognostic value. In meningiomas, MIB-1 correlates with recurrence, with a proposed 4.1% cutoff. This study aimed to identify optimal patient groups for the MIB-1 proliferation index threshold, hypothesizing improved recurrence prediction within stratified subgroups. We performed a retrospective cohort study of adult patients (≥ 18 years) undergoing primary meningioma resection (2005-2018) with available MIB-1 proliferation index and at least five years of MRI follow-up. Meningiomas of all WHO grades were included. Of 505 patients (median age 59 years) meeting inclusion criteria, 340 (67.3%) were female, with meningiomas predominantly WHO grade I (55.8%) or II (41.6%). subtotally resected (STR) WHO grade I meningiomas account for a total of 58 (20.6%) cases out of all 282 (GTR + STR) surgically treated grade I meningiomas. Of these 58 STR grade I meningiomas, 21 (36%) recurred within the 5-year follow-up period. Among 35 subtotally resected grade I meningiomas with MIB-1 values of ≤ 4%, only four (11%) recurred in five years. In the multivariable analysis, preoperative meningioma volume ((p = 0.02, HR 1.02) per 1 cm3 increase) and 4% cutoff for MIB-1 ((p = 0.02, HR 3.9) remained significant with respect to 5-year recurrence. Consistent with prior studies, the MIB-1 index of 4% seems to identify a subgroup of meningioma patients with low risk of recurrence. MIB-1 is likely to offer utility especially in designing individualized and less frequent imaging follow-up strategies after resection of WHO grade I meningiomas, where molecular genetics are not defined routinely.Clinical trial number: not applicable.