Assessment of MIB1 (Ki-67) Labeling Index and Correlation with Other Well Established Prognostic Factors in Breast Cancer

ABSTRACT

PURPOSE: The MIB1 labeling index is new method utilizing a monoclonal antibody against Ki-67 antigen and useful for evaluating the proliferation rate in breast cancer due to its ease of use and reliability. We compared the MIB1 labeling index to other, well established prognostic factors and assessed the prognostic value of MIB1 in 564 breast cancers. METHODS: The MIB1 (Ki-67 equivalent monoclonal antibody) proliferation rate, MIB1 labeling index, was determined in formalin-fixed, paraffin-embedded tissue specimens of 564 primary breast cancer patients who underwent surgery between March 1998 and February 2000 at Seoul National University Hospital. The clinicopathologic characteristics of the primary tumor such as age, tumor size, histologic type, nuclear grade, histologic grade, hormone receptor status and various tumor markers (p53, c-erbB-2, bcl-2) were compared with the value of the MIB1 labeling Index. RESULTS: The mean value of MIB1 labeling index was 6.9. MIB1 labeling index was correlated to younger age (p= 0.011), histologic types, low nuclear grade (p=0.0001), high histologic grade (p=0.0001), p53 positive (IDC) (p=0.0001), c-erbB-2 positive (DCIS) (p=0.01), comedo type (DCIS) (p= 0.001) and inversely correlated to hormone receptor positivity (p=0.0001), bcl-2 positive (IDC) (p=0.001). No correlation was found in tumor size, lymph node status and c-erbB-2 positive (IDC). CONCLUSION: The MIB1 labeling index correlated well with well-established poor prognostic factors. The MIB1 labeling index may be an important prognostic determinant in breast cancer.