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.