Low expression of Ki-67/MIB-1 labeling index in IDH wild type glioblastoma predicts prolonged survival independently by MGMT methylation status

Abstract

Purpose The Ki−67/MIB−1 labeling index (LI) is clinically used to differentiate between high and low-grade gliomas, while its prognostic value remains questionable. Glioblastoma (GBM) expressing wild-type isocitrate dehydrogenase IDHwt, a relatively common malignant brain tumor in adults, is characterized by a dismal prognosis. Herein, we have retrospectively investigated the prognostic role of Ki−67/MIB−1-LI in a large group of IDHwt GBMMethods One hundred nineteen IDHwt GBM patients treated with surgery followed by Stupp’s protocol in our Institution between January 2016 and December 2021 were selected. A cut-off value for Ki−67/MIB−1-LI was used with minimal p-value based approach.Results A multivariate analysis showed that Ki−67/MIB−1-LI expression < 15% significantly correlated with a longer overall survival (OS), independently from the age of the patients, Karnofsky performance status scale, extent of surgery and O6-methylguanine (O6-MeG)-DNA methyltransferase promoter methylation status.Conclusions Among others studies focused on Ki−67/MIB−1-LI, this is the first observational study showing a positive correlation between OS of IDHwt GBM patients and Ki−67/MIB−1-LI that we propose as a new predictive marker in this subtype of GBM