Abstract P6-05-07: Comparison of androgen receptor expression in core needle biopsies with surgical samples in primary breast cancer

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Abstract Background Breast cancer subtypes are important for the prognosis and optimal treatment of breast cancer patients. Moreover, these subtypes are determined by immunohistochemistry (IHC) using ER, PgR, HER2 and Ki-67 expressions in practical medicine. The androgen receptor (AR) is frequently expressed in breast cancer but has not yet been standardized. IHC is the standard procedure when using preoperative biopsy specimens to determine biomarker expressions. In this study, the differences in AR expression between core needle biopsy (CNB) and matched surgical samples were examined and the relationship between AR expression and the clinicopathological factors was investigated. Patients and Methods Primary breast cancer patients (n=432) who underwent surgery between March 2017 and June 2019 were diagnosed pathologically using CNB. The biomarker expression of 220 of the patients were determined using surgical samples without preoperative treatment. The AR expression was evaluated using IHC and the expression was divided into the negative, low (<10%) and high (≥10%) groups. The H-score (staining intensity x percentage of positive cells) was used to compare the extent of nuclear immunoreactivity for AR between CNB and the matched surgical samples in 119 CNB cases with an AR ≥ 10%. Breast cancer subtypes were categorized using the IHC data derived from ER/PgR, HER2 and Ki-67 (cutoff: 20%) values. Results 1. The AR positive rates was 57.5%(low: 10%; high: 47.5%)in all primary cases. AR expression significantly correlated with positive ER/PgR, lower Ki-67 values and nuclear grade, negative p53 and HER2. The AR expression rate was 73.4% in Luminal A, 59.3% in Luminal B, 65.2% in Luminal HER2, 43.3% in HER2 enriched and 22.2% in triple negative cases. 2. The AR positive rates of the matched cases were 65.0% in CNB cases (low: 10.9%; high: 54.1%) and 44.5% (low: 8.8%; high: 35.9%) in surgical sample cases (p<0.0001). However, there was no significant difference between AR expression and ER, PgR and HER2 status. Ki-67 index values were higher in the surgical samples (median: 35.0%) than CNB samples (median: 27.0%). 3. The median H-score was 130.0 (mean+/- SD: 143.2+/-63.0%) in CNB samples and 85.0 (mean+/-SD: 94.8+/-59.5%) in the surgical samples (p<0.0001), respectively. Conclusion A discordance in the AR expression and H-score between the core needle biopsies and matched surgical samples was found. These findings suggest that a fixation condition may affect the expression status after resection of samples. AR expression using IHC should be evaluated in core needle biopsies. However, further studies are needed for clinical use. Citation Format: Nobuyuki Arima, Reiki Nishimura, Tomofumi Osako, Yasuhiro Okumura, Masahiro Nakano, Mamiko Fujisue. Comparison of androgen receptor expression in core needle biopsies with surgical samples in primary breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-05-07.