Prognostic significance of Ki-67 antigen immunostaining (MIB-1 monoclonal antibody) in ovarian cancer.

OBJECTIVE To assess the potential usefulness of Ki-67 antigen expression as a predictor of outcome in ovarian cancer through the analysis of MIB-1 monoclonal antibody reactivity. METHODS Cell proliferation and clinicopathologic variables were assessed in 26 patients with primary epithelial ovarian cancer who had undergone exploratory laparotomy. The expression of primary tumor proliferation related to Ki-67 antigen was immunohistochemically evaluated by MIB-1 monoclonal antibody. RESULTS The value of Ki-67 labeling index (LI) ranged between 0 and 92.6% with a mean of 48.9%. Ki-67 LI correlated well with the mitotic index, but not the histological subtype. Ki-67 LI of more than 40%was defined as a higher proliferating tumor by a receiver operating characteristic curve analysis. Higher proliferating tumors were identified in 14 patients (54% of all subjects). The patients with higher proliferating tumors had a statistically significantly worse prognosis compared with those with lower proliferating tumors (p<0.001). CONCLUSIONS The present study demonstrates that the proliferating index detected by Ki-67 antigen immunostaining is a useful factor for predicting the survival of patients with ovarian cancer.