Cut-point for Ki-67 proliferation index as a prognostic marker for glioblastoma

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Abstract

Introduction

Ki-67 proliferation index (Ki-67 index) is used to quantify cell proliferation during histopathological assessment of various tumors including glioblastoma (GB).

Aim

We aimed to assess correlation between Ki-67 index and overall survival in patients with GB and determine a cut-point for Ki-67 index that predicts for poorer survival.

Method

Records of adult patients diagnosed with GB on histopathological specimens at a tertiary cancer center in Sydney between 1 January 2002 and 30 July 2012 were retrieved. Specimens of these patients were examined for quantification of Ki-67 staining by two independent pathologists. Patient, disease, treatment, and survival data were collected from hospital and cancer care service records. Statistical analysis was performed using proportional hazards models, Kaplan–Meier curves, and the minimum P-value approach.

Result

Of the eligible 71 patients, 58% were males with median age of 58 (range 18–87). Seventy-three percent of patients were of ECOG performance status 0–1. There was a statistically significant correlation between Ki-67 index and overall survival. In patients with Ki-67 > 22% (n = 36), 5-year survival was approximately 30% compared to 5% in those with Ki-67 ≤ 22% (n = 35; log-rank P-value = 0.04; hazard ratio (HR) = 0.53; 95% confidence intervals (CI), 0.29–0.97).

Conclusion

This study demonstrates a positive correlation between Ki-67 index and overall survival in patients with GB. Percentage staining of Ki-67 < 22% appears to predict for poorer survival in GB.

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