P46THE KI-67 LABELLING INDEX WITH MAXIMALLY SELECTED CUT-OFFS IS BETTER AT PREDICTING RECURRENCE THAN THE WHO GRADING SYSTEM OF MENINGIOMAS

摘要

INTRODUCTION: Meningiomas are principally benign tumours curable by resection. Many studies have shown a link between Ki-67 labelling indices (LI) and recurrence. Here we seek to improve the grading of meningioma through the use of LI with maximally selected cut points. METHOD: 285 adult meningiomas seen between 1999 and 2004 were examined immunohistochemically using the Ki-67/Mib-1 monoclonal antibody. Statistical analyses, were performed using R-Stats v2.15.1 and the R-Coin package. RESULTS: LI is associated with recurrence free survival (RFS) hazard ratio (HR) (1.09 p = 1.6x10⁻¹⁰). LI is correlated with tumour grade, there were significant differences between the LI means of each WHO grade (I - 4.9%, II - 12.3%, III - 28.7%; p = 2x10⁻¹⁶). Maximal selection of a cut point for RFS using multiple parameters revealed a cut point of LI 10%. Obtaining a further cut point on meningiomas with LI >10% gave the higher cut point of 27%. Kaplan-Meier (KM) analysis of WHO I - III showed a median RFS of 20.28, 8.79, & 1.14 years respectively (p = 3.7x10⁻⁸). KM analysis of cut point groups LI 1-10 (LI_A), 11-27 (LI_B), & >27 (LI_C) showed median RFS of 20.28, 7.96, & 1.99 years respectively (p = 6.9x10⁻¹³). Cox regression for RFS adjusting for age, gender, WHO grade & LI(A,B,&C) showed that with reference to WHO I, WHO II had a HR of 1.99 p = 0.03, grade III 4.25 p = 0.04; with reference to LI_A, LI_B had a HR of 2.3(1.15 - 4.7) p = 0.02 and LI_C a HR of 10.2(4 - 26) p = 1.2x10⁻⁶. CONCLUSION: These results demonstrated stratification, based solely upon the Ki67 labelling index, better predicting recurrence than the current WHO grading. This emphasises the need for LI to be fully incorporated into the grading system of meningiomas.