Abstract PO5-03-10: The prognostic role of androgen receptor status in patients with triple negative breast cancer with an associated ductal carcinoma in situ

Abstract Abstract Background Triple negative breast cancer (TNBC) is defined by the lack of expression of the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2. Prognostic immunohistochemical biomarkers in TNBC have been studied in recent years such as the androgen receptor (AR) which is expressed in 10-40% of TNBC. However the prognostic value of AR expression is not clear. Here, we studied the prognostic significance of AR expression in combination with the presence of a ductal carcinoma in situ (DCIS). Considering DCIS is a precursor of invasive ductal carcinoma, we hypothesize that TNBC with co-existing DCIS and presence of AR expression is less aggressive and patients are older at diagnosis. Methods We analyzed data retrospectively from all patients with stage 1-3 TNBC who underwent primary surgery and adjuvant chemotherapy in the University hospitals Leuven, between 01-01-2000 and 31-12-2017. Patient and tumor related characteristics were compared between two subgroups, one with co-existing DCIS and one with pure invasive carcinoma, without co-existing DCIS. AR expression was assessed by immunohistochemistry (IHC). We used AR expression in ≥1% and ≥10% of cells as cut-off scores. The prognostic role of the expression of AR in combination with a co-existing DCIS was analyzed, using the distant metastasis rate as primary endpoint. Results are presented as hazard ratios (HR) with 95% confidence intervals (CI). Secondary endpoints were associations of AR expression with clinical-pathological characteristics, time between diagnosis and metastasis, and disease specific mortality. Results In the 426 included patients with TNBC, co-existing DCIS was present in 66.7%; AR expression was expressed ≥1% in 29.3% and ≥10% in 21.4% of cases. Median age at diagnosis was 51 years (range: 22-85y). Age at diagnosis was independent of DCIS, dependent of AR expression; in DCIS positive cases, median age was 49 years if AR negative (IHC 1%), 53 years if AR positive (IHC ≥1%), and 56 years if AR positive (IHC ≥10%) (p=0.006). In contrast in DCIS negative cases, median age was 51 years if AR negative (IHC 1%), 51 if AR positive (IHC ≥1%), and 51 years if AR positive (IHC ≥10%) (p=0.895). AR expression was DCIS dependent and was ≥1% in 34.9% and ≥10% in 25.0% of patients in the DCIS group compared to 18.3% and 14.1% in the non-DCIS group (p=0.001 and p 0.001 respectively). In both subgroups there was no significant difference for AR positive versus AR negative cases in lymph node involvement, tumor grade, tumor size and Nottingham Prognostic Index. Patients with a coexisting DCIS and AR expression did not have a different incidence of distant relapse compared to AR negative cases (AR ≥1%: p=0.2803 and AR ≥10%: p=0.5527). Of patients with coexisting DCIS, 12.0% (95% CI: 7.8; 17.1) in the AR negative group, 8.2% (95% CI: 3.8; 14.6) in the AR ≥ 1% group and 7.1% (95% CI: 2.6; 14.7) in the AR ≥ 10% group, had distant relapse within 2 years. Conclusion In patients with TNBC, AR expression is associated with older age in case of co-existing DCIS and patients with co-existing DCIS are more frequently AR positive. In patients with co-existing DCIS, there was no significant difference in distant relapse between AR negative and AR positive cases. Citation Format: Micaëlle Merckx. The prognostic role of androgen receptor status in patients with triple negative breast cancer with an associated ductal carcinoma in situ 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 PO5-03-10.