Resected WHO grade I meningioma and predictors of local control.

INTRODUCTION: Despite optimal surgical resection, meningiomas may recur, with increasing grade and the degree of resection being predictive of risk. We hypothesize that an increasing Ki67 correlates with a higher risk of recurrence of resected WHO grade I meningiomas. METHODS: The study population consisted of patients with resected WHO grade 1 meningiomas in locations outside of the base of skull. Digitally scanned slides stained for Ki67 were analyzed using automatic image analysis software in a standardized fashion. RESULTS: Recurrence was observed in 53 (17.7%) of cases with a median follow up time of 25.8 months. Ki67 ranged from 0 to 30%. Median Ki67 was 5.1% for patients with recurrence and 3.5% for patients without recurrence. In unadjusted analyses, high Ki-67 (≥ 5 vs. < 5) vs. ≥ 5) was associated with over a twofold increased risk of recurrence (13.1% vs. 27% respectively; HR 2.1731; 95% CI [1.2534, 3.764]; p = 0.006). After Adjusting for patient or tumor characteristics, elevated Ki-67 remained significantly correlated with recurrence. Grade 4 Simpson resection was noted in 71 (23.7%) of patients and it was associated with a significantly increased risk of recurrence (HR 2.56; 95% CI [1.41, 4.6364]; p = 0.002). CONCLUSIONS: WHO grade 1 meningiomas exhibit a significant rate of recurrence following resection. While Ki-67 is not part of the WHO grading criteria of meningiomas, a value greater than 5% is an independent predictor for increased risk of local recurrence following surgical resection.