Thymidine labeling index and Ki-67 growth fraction in breast cancer: comparison and correlation with prognosis

In situ determination of proliferative activity was performed on 184 consecutive primary invasive breast cancers. Methods used were monoclonal antibody Ki-67 in immunohistochemistry and thymidine labeling index. Tumor proliferation correlated between both methods (p = 0.0001). For thymidine labeling index and Ki-67, respectively, significant correlations existed with histologic tumour grade and steroid hormone receptors (Tumor grade: TLI p = 0.0001; Ki-67 p = 0.0001. ER-ICA: TLI = 0.0001; Ki-67 p = 0.014. PgR-ICA: TLI p = 0.0001; Ki-67 p = 0.0008). For thymidine labeling index a significant correlation was demonstrated for overall survival (p = 0.001) and recurrence free survival (p = 0.01). No statistical significance was observed for clinical outcome and Ki-67 (overall survival p = 0.18; recurrence free survival p = 0.1). None of the factors, TLI or Ki-67, was an independent prognostic factor as demonstrated by multivariate analysis.