Prognostic role of Ki-67 in glioblastomas excluding contribution from non-neoplastic cells

Rikke H Dahlrot,Mia D Sørensen,Jeanette K Petersen,Steinbjørn Hansen,Bjarne W Kristensen,Julie A Bangsø,Guido Reifenberger,Ann Mari Rosager

doi:10.1038/s41598-021-95958-9

Abstract

Survival of glioblastoma patients varies and prognostic markers are important in the clinical setting. With digital pathology and improved immunohistochemical multiplexing becoming a part of daily diagnostics, we investigated the prognostic value of the Ki-67 labelling index (LI) in glioblastomas more precisely than previously by excluding proliferation in non-tumor cells from the analysis. We investigated the Ki-67 LI in a well-annotated population-based glioblastoma patient cohort (178 IDH-wildtype, 3 IDH-mutated). Ki-67 was identified in full tumor sections with automated digital image analysis and the contribution from non-tumor cells was excluded using quantitative double-immunohistochemistry. For comparison of the Ki-67 LI between WHO grades (II-IV), 9 IDH-mutated diffuse astrocytomas and 9 IDH-mutated anaplastic astrocytomas were stained. Median Ki-67 LI increased with increasing WHO grade (median 2.7%, 6.4% and 27.5%). There was no difference in median Ki-67 LI between IDH-mutated and IDH-wildtype glioblastomas (p = 0.9) and Ki-67 LI was not associated with survival in glioblastomas in neither univariate (p = 0.9) nor multivariate analysis including MGMT promoter methylation status and excluding IDH-mutated glioblastomas (p = 0.2). Ki-67 may be of value in the differential diagnostic setting, but it must not be over-interpreted in the clinico-pathological context.

Highlights

Survival of glioblastoma patients varies and prognostic markers are important in the clinical setting
In glioblastomas (WHO grade IV) the frequency of non-neoplastic cells varied from moderate (Fig. 1C) to high (Fig. 1D)
We found that cells with microglial cell and macrophage morphology expressed Ki-67 and that the fraction of these cells increased with increasing World Health Organization (WHO) grade

Summary

Introduction

Survival of glioblastoma patients varies and prognostic markers are important in the clinical setting. With digital pathology and improved immunohistochemical multiplexing becoming a part of daily diagnostics, we investigated the prognostic value of the Ki-67 labelling index (LI) in glioblastomas more precisely than previously by excluding proliferation in non-tumor cells from the analysis. Other important prognostic biomarkers for patients with diffuse astrocytic and oligodendroglial tumors include isocitrate dehydrogenase (IDH) mutation, 1p/19q codeletion and histone 3 K27M m utation[8] These three molecular alterations have since 2016 been used as strong defining diagnostic markers for the distinction of biologically and clinically distinct glioma entities in the revised World Health Organization (WHO) classification of central nervous system tumors 20169. Other groups reported that Ki-67 LI was not associated with OS3,19,31–34 These previous studies on Ki-67 did not include MGMT promoter methylation status and post-surgical treatment in the survival analysis these parameters have significant prognostic impact on the outcome in the glioblastoma patients

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