Prognostic Significance of Ki-67 Antigen Immunostaining (MIB-1 Monoclonal Antibody) in Ovarian Cancer

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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.