Ki-67 labeling is correlated with the time to recurrence in primary glioblastomas

The Ki-67 labeling index (LI) was shown in many cut-off studies to be significantly correlated to the postoperative survival probability in gliomas in univariate and multivariate analyses. However, a direct relationship of the Ki-67 LI and the growth fraction, respectively, to clinical growth parameters was not demonstrated in a single tumor type of this group until now. We compared the Ki-67 LI of 20 primary glioblastomas and their recurrent tumors with the time to reoperation for recurrence. Regression analyses showed (1) a high reproducibility of the LIs at the second versus the first operation corresponding to an inherent growth potential of a given individual tumor and (2) a strong inverse correlation of LI to time to recurrence (TR) (r = -0.92). Additionally to a lower LI (corresponding to a smaller growth fraction), a longer cycle time could be derived in slowly growing as compared to rapidly growing tumors. A direct relationship of the Ki-67 LI to a clinical time parameter (the TR) was obtained, and a predictive significance of individual LIs in glioblastomas could be defined.