Abstract P4-09-02: Prognostic and Predictive Value of Centrally Reviewed Ki67 Labeling Index in Postmenopausal Women with Endocrine-Responsive Breast Cancer: Results from Austrian Breast and Colorectal Cancer Study Group Trial 8

Abstract

Abstract Purpose: The aim of the present study was to assess the prognostic and predictive value of Ki67 labeling index in postmenopausal hormone receptor-positive early breast cancer patients who were treated with adjuvant tamoxifen or anastrozole after tamoxifen. Patients and Methods: We determined the expression of Ki67 by immunohistochemistry on whole tissue sections of breast carcinoma patients who had been enrolled in Austrian Breast and Colorectal Cancer Study Group (ABCSG) Trial 8 and received tamoxifen for 5 years or tamoxifen for 2 years followed by anastrozole for 3 years. Ki67 labeling index was evaluated as continuous variable or dichotomized at 10%. Distant recurrence and death were analyzed using Cox models adjusted for clinical and pathological factors. Results: High Ki67 labeling index was observed in 394 of 1587 (23%) tumors and was associated with poor outcome. Patients with high Ki67 labeling index had a significantly shorter distant recurrence-free survival (adjusted hazard ratio [HR] for distant recurrence 2.16, 95% confidence interval [CI] 1.43-3.25, P < 0.001) and overall survival (adjusted HR for death 1.77, 95% CI 1.30-2.42, P < 0.001) as compared to patients with low Ki67 labeling index. No interaction between Ki67 labeling index and treatment was observed (P = 0.84). Conclusion: High Ki67 labeling index is an independent poor prognostic factor for distant recurrence and death in postmenopausal women with early-stage, hormone receptor-positive breast cancer but is not predictive for outcome of adjuvant treatment with either tamoxifen or tamoxifen followed by anastrozole. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-09-02.