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

Assess impact of K -67 labeling index (LI; K -67 LI) on risk of recurrence or progression of WHO grade I meningiomas.  Retrospective study of adult patients who underwent resection of cranial base meningioma between 2004 and 2016.  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 -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 -67 LI, those with intermediate K -67 LI had 2.47 times (2.47 [1.09-5.59],  = 0.03), and those with high K -67 LI had 3.38 times (3.38 [1.16-9.89],  = 0.03) higher risk of recurrence or progression. Tumors with K -67 LI > 4% had a shorter time to recurrence or progression (  = 0.01). Recurrence or progression-free survival rates at 3, 5, and 10 years for tumors with low K -67 LI were 95%, 89%, and 75%, respectively; tumors with intermediate K -67 LI, 87%, 69%, and 52%, respectively; tumors with high K -67 LI, 78%, 49%, and 49%, respectively.  Following surgical resection of a WHO grade I cranial base meningioma, K -67 LI > 4% may predict an increased risk of recurrence or progression of residual tumor.