Ki-67 labeling index in glioblastoma; does it really matter?

Objective/background: Glioblastoma (GB) is the most common primary malignant brain tumor in adults. Ki-67 is a nonhistone nuclear protein that is expressed by cells entering the mitotic cycle and is associated with the transcription of ribosomal RNA (rRNA). In gliomas, the extent of expression of Ki-67 is roughly proportional to the histologic grade. Over the years, association studies were conducted trying to link the poor outcome in different types of malignant tumors to the Ki-67 proliferative index. This study is designed to investigate the relationship between the proliferation marker, Ki-67, and the overall survival amongst glioblastoma patients diagnosed between 2006 and 2012 at a single institution in Riyadh, Saudi Arabia.

Methods: This is a retrospective cohort study which investigated the status of Ki-67 labeling index in glioblastoma patients diagnosed at King Abdulaziz Medical City, Riyadh, Saudi Arabia, between 2006 and 2012. The Kaplan-Meier survival analysis was used to assess the overall survival (OS) and the Mantel-Cox log-rank test was used to compare the survival curves. Multivariate analysis using Cox proportional-hazards model was used to investigate other factors that might influence the overall survival.

Results: A total of 44 glioblastoma patients were included in the study. The median age at diagnosis was 56 (1-91) years. The 12-month survival rate for all glioblastoma patients was 48%. The median survival for patients with Ki-67 labeling index of ≤27%, and >27% was 11 months and 14 months, respectively.

Conclusion: The difference between the survival curves of patients with Ki-67 labeling index of ≤27%, and Ki-67 of >27% was statistically insignificant (p = .130). Therefore, Ki-67 labeling index alone cannot predict survival in glioblastoma patients.