Value of K _i -67 Labeling Index in Predicting Recurrence of WHO Grade I Cranial Base Meningiomas

Objectives  Assess impact of K _i -67 labeling index (LI; K _i -67 LI) on risk of recurrence or progression of WHO grade I meningiomas. Study Design  Retrospective study of adult patients who underwent resection of cranial base meningioma between 2004 and 2016. Results  272 patients fulfilled criteria for inclusion in the study. Average age was 61.8 years; 196 (72%) were females. Simpson's grade 1 resection was noted in 77 patients (32%), grade 2 in 39 (16%), grade 3 in 36 (15%), and grade 4 in 88 (37%). The K _i -67 LI was low (1-4%) in 214 (78.7%), intermediate (5-9%) in 44 (16.2%), and high (>10%) in 14 (5.2%). Median follow-up was 39 months (IQR: 16-71 months); 221 (87.1%) tumors remained stable or did not recur, 19 (7.4%) recurred, and 14 (5.5%) progressed. Compared with tumors with low K _i -67 LI, those with intermediate K _i -67 LI had 2.47 times (2.47 [1.09-5.59], p  = 0.03), and those with high K _i -67 LI had 3.38 times (3.38 [1.16-9.89], p  = 0.03) higher risk of recurrence or progression. Tumors with K _i -67 LI > 4% had a shorter time to recurrence or progression ( p  = 0.01). Recurrence or progression-free survival rates at 3, 5, and 10 years for tumors with low K _i -67 LI were 95%, 89%, and 75%, respectively; tumors with intermediate K _i -67 LI, 87%, 69%, and 52%, respectively; tumors with high K _i -67 LI, 78%, 49%, and 49%, respectively. Conclusions  Following surgical resection of a WHO grade I cranial base meningioma, K _i -67 LI > 4% may predict an increased risk of recurrence or progression of residual tumor.