Is androgen receptor useful to predict the efficacy of anti-estrogen therapy in advanced breast cancer?

1042 Background: The androgen receptor (AR) is widely expressed in breast cancers but its role in estrogen receptor (ER)-positive tumors is still controversial. However, the AR/ER ratio may impact prognosis and the response to antiestrogen endocrine therapy (ET). Methods: We assessed whether AR in primary tumors and/or matched metastases is a predictor of efficacy of first-line ET in advanced breast cancer (ABC). We evaluated patients treated with first-line ET (2002–2011), excluding those receiving concomitant chemotherapy or trastuzumab or pretreated with > 2 lines of chemotherapy. ER, progesterone receptor (PgR), Her2, Ki67 and AR expression was determined by immunohistochemistry. A cut-off of < 1% immunostained cells was used to categorize AR expression. AR expression was analyzed in relation to the other conventional biomarkers (ER, PgR, Her2 and Ki67), best response (CR, PR, SD, PD), and time to progression (TTP) (months). TTP was estimated using the Kaplan-Meier method and compared with the log-rank test. Hazard ratios and their 95% confidence intervals (95% CI) were estimated using the Cox regression model. The Chi-square test was used to evaluate correlations between categorical variables and best response. p values < 0.05 were considered statistically significant. Results: Of the 102 evaluable patients (93% were treated with an aromatase inhibitor), biomarkers were assessed in primary tumors in 70 cases, in metastases in 49 and in 17 in both). Median TTP was 17 months (95% CI 14-21.5, median follow-up 75 months). The overall concordance rate between primary tumors and metastases was 64.7% (95% CI 42%-87.4%) for AR expression. Differences in TTP according to AR status were not statistically significant. AR/PgR ≥ 0.96 was associated with a significantly shorter TTP (HR = 1.65, 95% CI 1.05-2.61, p = 0.030). AR status in primary tumors or metastases was not associated with PD as best response. In contrast, Ki67 > 20% and PgR < 10% showed a significant association with PD as best response. Using a cut off of ≤10% for AR expression, results did not change. Conclusions: AR expression does not appear to be useful to predict the efficacy of ET in ABC. Ki67 and PgR exert a greater impact on the efficacy of hormone therapy than AR.