Abstract 5173: Androgen receptor status is highly conserved during tumor progression of breast cancer

Abstract

Abstract Introduction: Many clinical trails are ongoing targeting androgen receptor (AR) in breast cancer (BC). Anti-androgen therapy is increasingly accepted in BC patients since the new compounds have less androgenic side effects. The assessment of AR status is generally performed on the primary tumor even when treating metastatic disease. To the best of our knowledge, nothing is known regarding discrepancies of AR status between the primary tumor and the metastatic site. Therefore, we investigated AR status on a large cohort of primary BCs and matched metastases. Method: A next-generation Tissue Microarray (ngTMA) was constructed harboring 356 primary BCs, 133 matched metastases and 11 recurrences. A commercially available monoclonal AR antibody (DAKO) was used to evaluate AR-Status by immunohistochemistry. AR positivity was defined as ≥1% of nuclear staining in tumor cells. The results of the primary tumor and metastases/recurrences were compared. Additionally, the results of AR status were correlated with other pathological tumor features. Result: AR could be evaluated in 353/356 (99.2%) of primary BCs and a positivity was detected in 307 (87%). A discordant result was seen in 4.3% metastasized BC's with informative results (5/117). Three negative BCs were positive in the metastases representing 16.7% of all negative BCs with informative results (3/18). Two BCs were positive in the primary and negative in the metastases representing 2.0% of all positive BCs with metastases and informative results (2/99). No discrepancies were seen between primary and loco-regional recurrences. Further, AR expression was significantly correlated with a positive estrogen (p<0.001) and progesterone receptor (p<0.001) status and a low proliferation (≤15%) (p<0.001). Negative AR status was significantly (p<0.001) associated with a higher tumor grade. Triple negative BCs were in 11.4% AR positive (4/35). Conclusion: AR positivity is frequent in primary BCs (87%) and AR status is highly conserved during tumor progression. In a small fraction AR status changes (4.3%) either from positive to negative status or vise versa. However, even AR status is highly preserved we would recommend reevaluation of the metastatic site in negative BC's since a positive AR status can be seen in 16.7% of this subgroup. Citation Format: André Grogg, Katrin Pfaltz, Claudia Lädrach, Nikola Cihoric, Martin Zweifel, Coya F. M. Tapia. Androgen receptor status is highly conserved during tumor progression of breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5173. doi:10.1158/1538-7445.AM2015-5173