Prognostic value of Ki-67 proliferating index in triple negative breast carcinomas

The aim of this study was to assess Ki-67 in the triple negative breast cancer group (TNBC) in addition to basal like (BL) immunophenotype, BL morphology and conventional clinicopathologic factors, and to demonstrate their prognostic relevance in this group of tumors. Immunohistochemical staining for CK5/6, CK14, EGFR and Ki-67 was performed on 83 formalin-fixed, paraffin-embedded tumor sections. Correlations between categorical variables were studied using the chi-square and the Mann-Whitney U test. For survival analysis, the Kaplan-Meier method, the log-rank test and the Cox proportional hazard regression model were used. The optimal cut-off values for Ki-67 and mitotic count were selected using the ROC (receiver operating characteristic) method. Of the 83 TNBC, 55 (66.3%) had the BL immunophenotype, and 40 (48.2%) had BL morphology. Clinical stage and Ki-67 proliferation index were significantly associated with shorter disease-free survival (DFS) (p=0.002 and p<0.001) and overall survival (OS) (p=0.05 and p=0.025). An independent prognostic relevance regarding DFS and OS was found for clinical stage (p<0.001 and p<0.001), Ki-67 (p=0.008 and p=0.055) and BL morphology concerning DFS (p=0.011). Cellular proliferation measured by Ki-67 has prognostic relevance in TNBC, but further validation of its clinical significance, standardization of assessment and determination of optimal cut-off points is essential for this group of breast tumors.