5 Background: Triple-negative breast cancer (TNBC) is an immunogenic breast cancer subtype, with a greater percentage of tumors containing tumor-infiltrating lymphocytes (TILs) compared to non-TNBC. TILs are prognostic for recurrence and predictive for chemotherapy benefit in TNBC, but not in estrogen receptor (ER)-positive tumors. A subset of TNBC expresses the androgen receptor (AR), and resembles ER-positive breast cancer in terms of demographics (older age) and clinical course (later recurrences that tend to involve bone). However, little is known regarding the association between TILs and AR expression in TNBC. Methods: From a cohort of 9982 women with surgically-treated non-metastatic breast cancer, patients who met criteria for TNBC (ER/PR < 1% and HER2-negative) by centralized-pathology review were included as previously published [Leon-Ferre et al, Breast Cancer Res Treat 2017]. Stromal TILs in these tumors were quantified on full-face hematoxylin and eosin sections from the surgical specimen, following the 2014 TIL Working Group recommendations [Salgado et al, Ann Oncol 2014]. The expression of AR [EPR1535(2), Abcam] was scored as a continuous variable (1% increments), and categorized as absent (0%), low (1-25% ), low-moderate (26-50%) moderate (51-75%) and high (> 75%) and correlated with TIL density. Results: 605 patients met criteria for TNBC. The median age was 56 years. Most tumors were T1-2 (95%), N0-1 (86%), and high grade (88%). The median stromal TIL content was 20% (0-90%). Tumor tissue was available for AR staining in 509/605 patients. 165 (32%) tumors expressed AR as follows: low: 12%, low-moderate: 7%, moderate: 5%, and high: 8%. Apocrine tumors (n = 30) expressed AR most frequently (86%) and at higher levels (AR high: 50%). For all 509 tumors, the median stromal TIL content according to AR expression was AR absent: 20%, AR low: 20%, AR low-moderate: 15%, AR high: 10%. AR and stromal TILs (both as continuous variables) demonstrated a weak inverse correlation (correlation coefficient -0.1064, p = 0.017). Conclusions: AR expression in TNBC is associated with lower levels of stromal TILs. Additional data correlating the AR, stromal TILs and outcomes in this cohort will be presented at the meeting.
Clinico-pathological relationship between androgen receptor and tumour infiltrating lymphocytes in triple negative breast cancer
