Higher expression of androgen receptor is a significant predictor for better endocrine-responsiveness in estrogen receptor-positive breast cancers.

The aim was to investigate the implications of androgen receptor (AR) expression levels on outcomes for estrogen receptor (ER)-positive tumors. Immunohistochemically AR levels were determined from tissue microarrays of 614 ER-positive patients who received adjuvant endocrine with or without chemotherapy between November 1999 and August 2005. Characteristics and survival were analyzed using a Chi-square test, Kaplan-Meier methods, and Cox's models. AR levels were categorized into 3 subgroups as follows: low, AR < 10%; intermediate, 10% ≤ AR < 50%; high, AR ≥ 50%. Low, intermediate, and high AR levels were observed in 29.0, 44.0, and 27.0% of patients, respectively. High AR was associated with smaller size, nodal uninvolvement, grade I/II tumor, higher progesterone receptor expression, and lower proliferation index. With a median follow-up of 70.9 months, the high AR subgroup showed better survival, and these associations were maintained in 119 patients who received endocrine therapy alone [hazard ratio (HR), 0.111; 95% CI, 0.013-0.961 for disease-free survival (DFS); HR, 0.135; 95% CI, 0.015-1.208 for overall survival (OS)]. No significant benefits from chemotherapy were demonstrated in the high AR subgroup; however, the benefit from chemotherapy was significant among 448 AR-intermediate or -low patients (HR, 2.679; 95% CI, 1.452-4.944 for DFS; HR, 3.371; 95% CI, 1.611-7.052 for OS). High AR is an independent prognostic factor and a significant predictor for better endocrine-responsiveness in ER-positive tumors. AR-low or -intermediate levels could give an additional indication for use of chemotherapy in ER-positive tumors.