Low p27 Expression Predicts Early Relapse and Death in Postmenopausal Hormone Receptor–Positive Breast Cancer Patients Receiving Adjuvant Tamoxifen Therapy

Purpose: Previously, we have shown that p27 may be a potential predictive biomarker for the selection of premenopausal women with early-stage hormone-responsive breast cancer for adjuvant endocrine therapy. The purpose of the present study was to assess the clinical relevance of p27 expression in postmenopausal hormone receptor–positive breast cancer patients who were treated with adjuvant tamoxifen therapy. Experimental Design: We determined the expression of p27 by immunohistochemistry in the surgical specimens of breast carcinoma patients who had been enrolled in Austrian Breast and Colorectal Cancer Study Group Trial 06 and received tamoxifen for 5 years. Early relapse and death within the first 5 years of follow-up were analyzed using Cox models adjusted for clinical and pathologic factors. Results: p27 expression was high (>70% p27-positive tumor cells) in 252 of 483 (52%) tumor specimens and was associated with favorable outcome of the patients. Women with high p27 expression had a significantly longer disease-free survival (adjusted hazard ratio for relapse, 0.22; 95% confidence interval, 0.11-0.42; P < 0.001) and overall survival (adjusted hazard ratio for death, 0.39; 95% confidence interval, 0.21-0.72; P = 0.002) as compared with women with low p27 expression. Conclusion: Low p27 expression independently predicts early relapse and death in postmenopausal women with early-stage, hormone receptor–positive breast cancer who received adjuvant tamoxifen for 5 years. (Clin Cancer Res 2009;15(18):5888–94)