MIB-1 PROLIFERATION INDEX PREDICTS SURVIVAL AMONG PATIENTS WITH GRADE-II ASTROCYTOMA

The purpose of this study was to determine whether a relationship exis ted between MIB-1 labeling index (LI) percentages and survival in pati ents with grade II astrocytomas. From archival paraffin-embedded surgi cal specimens of 50 patients of the University of Michigan Medical Cen ter with World Health Organization grade II astrocytomas, 22 patients had a Ki-67 LI of less than or equal to 2.0; and 28 patients had a MIB -1 LI of more than 2.0. Over a median follow-up interval of 10 years, ranging up to 16 years, 23% (n = 5) died of tumor in the first group w hile 82% (n = 23) died in the second group, a distinct difference in s urvival between these groups. Univariate analysis showed that a high M IB-1 predicted shorter survival (p < 0.0001), and that increased age w as associated with shorter survival (p = 0.007). Gender, tumor locatio n and radiotherapy had no significant association with survival. When adjusting for these (excluding tumor location) in the Cox proportional hazards model simultaneously, MIB-1 and age were independently progno stic. The hazard ratios were 1.301 per 1% MIB-1 LI (p = 0.0001), and 1 .045 per year of age (p = 0.0028). From other studies, we know that hi stopathologic grade and age predict survival for glioma patients. Howe ver, even within grade II astrocytomas there is still a wide heterogen eity in how long a patient survives. We conclude that among grade II a strocytomas older patients and, independently, patients with higher MI B-1 labeling index have shorter survival.