COMPARATIVE PROGNOSTIC VALUE OF KI-67 AND MIB-1 PROLIFERATION INDEXESIN BREAST-CANCER

Background. Tumor proliferation index was evaluated in 246 samples of breast carcinoma using Ki-67 and MIB-1 monoclonal antibodies on frozen and paraffin sections, respectively with the purpose to compare the t wo proliferation indices from both a quantitative and prognostic point of view. Materials and Methods. All determinations were performed wit h the same immunohistochemical procedure (Avidin-Biotin Complexes). Th e prognostic relevance of tumor proliferation index, defined by both t he antibodies, was investigated in 127 patients. Ki-67 and MIB-1 media n values were used to obtain two groups of patients at differ ent risk and life-table analysis (Mantel-Cox) was performed to assess the prob abilities of overall survival (OS) and relapse-free survival (RFS). Th e median time of observation was 61 months. Results. Ki-67 and MIB-1 v alues were exponentially distributed with overlapping ranges varying f rom 2% to 90%. Ki-67 mean and median values were 16.7% and 14.0%, resp ectively, compared to 22.5% and 20% for MIB-1. Ki-67 and MIB-1 mean va lues were statistically different (t = 4.396; p < 0.001), while no dif ference was observed for MIB-1 mean values on frozen and paraffin sect ions (t = 1.35; p = n.s.). Ki-67 and MIB-1 values were statistically c orrelated (Spear-man's coefficient = 0.75; p < 0.0001) and directly as sociated (agreement rate = 79.3%; p < 0.0001). Patients with tumors ha ving a high proportion of MIB-1 positive cells showed a higher 5-year probability of relapse of disease (43.7% versus 27.6%; p = 0.02) and d eath (35.4% versus 15.8%; p = 0.007) than those with a low one. In par allels Ki-67 was found to be prognostically relevant for OS (32.2% ver sus 16.2%; p = 0.02) but not for RFS (40.7% versus 27.9%; p = 0.10). C onclusions. Such results indicate that the detection of proliferative activity on paraffin sections with MIB-1 monoclonal antibody provides in formation analogous to or even better than that obtained with Ki-67 antibody on frozen ones. Moreover, it represents a valuable fool to o btain kinetic data on ''routine'' histological samples and above all, to give prognostic evaluations on the clinical outcome of breast cance r patients.