Abstract PO2-14-07: Association between expression of androgen receptor in tumor tissue and risk of breast cancer recurrence among premenopausal Danish women

Abstract Background: Breast cancer prognosis is influenced by tumor biomarker expression. For example, tumors that express the estrogen receptor (ER+) have a lower hazard of recurrence in the first five years following treatment than tumors that do not express the estrogen receptor. Identifying additional biomarkers that are prognostic of breast cancer recurrence may aid in risk stratification and the development of targeted therapies. The androgen receptor (AR) is one such candidate biomarker. While some previous studies have found lower breast cancer mortality associated with AR expression, others have shown no association. However, these studies were conducted in populations exclusively or primarily comprised of postmenopausal women. Since menopause is associated with an increased concentration of androgens relative to estrogens, the role of AR may differ in premenopausal women. Methods: Using the Predictors of Breast Cancer Recurrence cohort (N=5,959)—a prospective cohort study of premenopausal women diagnosed with stage I–III primary breast cancer between 2002 and 2011 and registered in the Danish Breast Cancer Cooperative Group (DBCG) clinical database—we measured the association between tumor AR expression and breast cancer recurrence. The majority of the cohort (77%) had ER+ tumors and were intended to be treated with tamoxifen. Primary paraffin-embedded tumors were collected from treating hospitals, and 2–3 cores were included in a tissue microarray for immunohistochemistry. AR staining of each core was automatically scored using a trained software application and quantified as the percent of tumor nuclei with positive staining. Patients were considered to have AR positive (AR+) tumors if the maximum score across replicate cores was 1% positive. Otherwise patients were classified as having AR negative (AR−) tumors. Patients were followed from breast cancer diagnosis until the first of recurrence, death, emigration, another malignancy, or 10 years. The DBCG defines breast cancer recurrence as any breast cancer diagnosed after the initial course of treatment, including contralateral breast cancers. The association between AR expression and breast cancer recurrence was computed as an unadjusted risk ratio and corresponding 95% confidence interval. Results: Among the 4,658 cohort members with available tumor tissue, 72% had AR+ tumors; 720 recurrences occurred over the 10-year follow-up. Patients with AR+ tumors were less likely to experience a recurrence than patients with AR− tumors 14% vs. 18% respectively; unadjusted risk ratio=0.80, 95% CI: (0.70, 0.92). Conclusion: AR expression in primary tumor tissue was associated with a lower risk of breast cancer recurrence in a large population-based cohort of premenopausal women. Additional analyses adjusting for clinical factors, examining the association by breast cancer subtype, and accounting for time to recurrence are forthcoming. Citation Format: Rebecca Nash, Anders Kjærsgaard, Kristina Christensen, Thomas Ahern, Lindsay Collin, Stephen Hamilton-Dutoit, Lauren McCullough, Joellen Schildkraut, Henrik Sørensen, Kevin Ward, Kirsten Woolpert, Timothy Lash, Deirdre Cronin-Fenton. Association between expression of androgen receptor in tumor tissue and risk of breast cancer recurrence among premenopausal Danish women abstract. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-14-07.