Prognostic Value of mib-1 in Patients with Early Invasive Breast Cancer and Its Correlation with Other Biologic Parameters in a Monoinstitutional Series

INTRODUCTION: Mib-1 is a proliferation biomarker and a prognostic factor for breast cancer as reported in several studies.PURPOSE: The aim of the present study was to examine interactions between mib-1 and other clinical-pathological markers and their impact on outcomes in early invasive breast cancer.PATIENTS AND METHODS: Mib-1 was identified by immunohistochemical staining in 2660 EIBC patients treated in our institution from 2000 to 2008. Mib-1 was dichotomized at the value of 20%. Correlation between mib-1 (> or ≤10620%) and age, tumour size (T), nodal status (N), ER, PR, HER-2, grading (G) was performed by χ2 test. Log-rank test and Cox regression model were performed to test mib-1 as prognostic factor for overall survival (OS) and Disease Free Survival (DFS) and evaluate its correlation with other known prognostic factors.RESULTS: Mib-1 was > 20% in 1276 and ≤106 20% in 1384. Mib-1> 20% was significantly (p=.000) associated with younger age, greater size, positive lymph nodes, poor grading, absent or low ER and/or PR expression level, HER-2 over-expression or amplification with or without co-expression of ER and/or PR, triple negative subtypes. Mib-1 was a significant predictor of worse DFS and OS (p=.000). At a median follow up of 32 months the DFS and OS were 97.4 and 99.2% respectively in Mib-1 ≤20% group and 92.4 and 97.2% respectively in Mib-1 > 20%. There were 195 relapses (7,3%): 139 (5.2%) in Mib-1 > 20% and 56 (2.1%) in Mib-1 ≤ 20%. Breast cancer related deaths were 74 (2.8%) with 58 (2.2%) in mib-1 > 20% group and 16 (0.6%) in mib-1 ≤ 20%.Mib1 >20% was predictive of poorer prognosis in > 40 years patients, small tumors (T1), lower grading (G1 and G2), positive ER and/or PR group with high or intermediate expression, negative HER-2 tumors. However, in Cox multivariate analysis mib-1 didn't maintain independent prognostic value.CONCLUSIONS: In our experience, Mib-1 confirms to be a significant prognostic biomarker for DFS and OS in early breast cancer. It could provide additional information beside other clinico-pathological parameters to perform the risk stratification of early breast cancer patients.