Correlation of Ki-67 Index with Volumetric Segmentation and its Value as a Prognostic Marker in Glioblastoma

Previous research has shown a strong correlation between the Ki-67 proliferation index and grade of malignancy in astrocytoma. Ki-67 has also shown encouraging results as a prognostic marker for patients' overall survival (OS). We focus on whether the index is linked to the appearance of glioblastoma on pretreatment magnetic resonance imaging (MRI) or to OS.

In our retrospective study, only isocitrate dehydrogenase IDH wild-type glioblastoma was included (n = 152). Ki-67 index was quantified via immunohistochemistry. On all pretreatment MRI, tumor compartments (tumor, necrosis, and edema) were volumetrically assessed. An OS subpopulation was filtered from the total cohort (residual tumor volume ≤2 cm³). In addition, a propensity score matching was executed.

All volumetric assessed tumor volumes correlated with each other (P ≤ 0.011), although the Ki-67 index showed no correlation with any of the measured volumes. Concerning the OS, a cutoff value of 20% for the Ki-67 index showed a significant influence on patients' OS in multivariate analysis (P = 0.043).

The unique appearance of every glioblastoma on MRI seems to be independent of the Ki-67 index. Furthermore, the Ki-67 index did show a distinct prognostic value for OS within our cohort at a cutoff value of 20% for Ki-67.