Abstract P5-05-11: Clinical significance of androgen receptor expression in breast cancer

Abstract

Abstract Background Breast cancer is highly heterogeneous and immunohistochemistry (IHC) is used to determine breast cancer subtypes using estrogen and progesterone receptor (ER and PgR), HER2 and Ki-67. The androgen receptor (AR) is frequently expressed in breast cancer, but evaluation of AR has not been standardized and the oncogenic activity in breast cancer is still unclear. The objectives of this study were to assess the clinical significance of AR expression in breast cancer patients with primary (pretreatment and posttreatment) and recurrent breast cancer in relation to breast cancer subtype. Methods Primary and recurrent breast cancer patients who underwent treatment from March 2017 to May 2018 were enrolled in this study. A total of 591 primary breast cancer cases and 52 recurrent cases were analyzed. Thirty-four primary cases received treatment before surgery. The factors investigated included nodal status, tumor size, nuclear grade, ER/PgR and HER2 status, p53 overexpression, and the Ki-67 index value. The AR expression was evaluated using IHC and the expression was divided into 3 groups; negative, low (<10%) and high (≥10%). Breast cancer subtypes were categorized based on the IHC data derived from ER/PgR, HER2 and Ki-67 (cutoff point: 20%) in invasive tumors. Results The AR expression rates were 69.7%(low: 33.9% and high: 35.8%)in all primary cases. Patients who received treatment before surgery had an AR rate of 38.2% which was significantly different from the untreated cases (p=0.002). In the cases with neoadjuvant chemotherapy, the positive rate significantly decreased after chemotherapy in the cases with non-pCR (pathological complete response). The positive rate of recurrent/metastatic cases was 57.7% (low: 34.6% and high: 23.1%). Higher AR expression significantly correlated with smaller tumor size, positive ER/PgR, lower Ki-67 values and nuclear grade and negative p53 overexpression. The AR expression rate was 72.5% in Luminal A, 73.2% in Luminal B, 80% in Luminal HER2, 56.8% in HER2 enriched and 43.5% in triple negative (TN) cases. Moreover, in the TN tumor cases, AR expression significantly correlated with postmenopausal status and a higher degree of malignancy determined by Ki-67, p53, and nuclear grade. However, there was no significant relationship between these factors and the other subtypes. Conclusion The AR expressions were higher in the primary breast cancer cases than in the pretreated and recurrent cases. The AR expression significantly correlated with a lower degree of malignancy and postmenopausal status only in the TN breast cancer cases. These findings suggest that the TN cases with AR-positive tumors have a more favorable prognosis compared with the cases with AR-negative tumors. However, further studies are needed to determine the predictive and prognostic factors for clinical use. Citation Format: Arima N, Nishimura R, Osako T, Okumura Y, Nakano M, Fujisue M. Clinical significance of androgen receptor expression in breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-05-11.