Correlation Between Ki-67 Index and Patient Survival in Glioblastoma Multiforme

Introduction :  Glioblastoma multiforme (GBM) is a class IV astrocytic tumor, the most malignant of the four groups of tumors with astrocytic differentiation as per the revised 2016 WHO classification of CNS tumors. Historically, patients with GBM have had a very poor survival rate. The aim of this study was to establish whether a correlation between the Ki-67 index of GBM tumor samples and patient survival exists. Materials and Methods:  Forty-one GBM tumor samples were tested for their IHC reaction with Ki-67 after their original H&E and other IHC slides were reviewed by a single author and blind coded to ensure non-suggestive analysis of the results. The Ki-67 positivity index of the nuclei was estimated after digitalization of the slides, using the Leika Aperio AT2 slide scanner and calculated by the ImmunoRatio automated counting tool on the digital slides. The individual Ki-67 index and patient survival of each case were statistically compared after the cases were decoded. Results :  The forty-one GBM cases had a mean Ki-67 index of 17.34%, standard deviation ±10.79 (p>0.05), with the lowest index being 2% and the highest one being 46%. Statistical analysis of the Ki-67 index divided dichotomously into two groups (low and high) and patient survival revealed that cases with a high Ki-67 index had no significant difference in survival when compared to those with low expression. Conclusion :  Based on the reported results the mean Ki-67 percentage of positive nuclei in GBM tumor samples cannot be used to estimate the survival of patients. However, Ki-67 remains a valuable IHC tool in pathology.