Androgen receptor expression is useful to predict the therapeutic effect in HER2-positive breast carcinoma

Purpose Although HER2-positive (HER2+) invasive breast carcinomas (BC) have a different clinical therapeutic responsiveness according to estrogen and progesterone receptor expression, the relationship with androgen receptors (AR), which are the same family of steroid hormones, is poorly understood. We investigated the relationship between AR expression in HER2 BCs and therapeutic responsiveness and prognosis in this study. Methods We evaluated patients with HER2 (H) + invasive BC undergoing surgery after neoadjuvant chemotherapy (+/- HER2-targeted therapies) from 2007-2017, classified as hormone receptor-positive (Allred score: 2-8) (luminal B: LH) and receptor-negative groups (Allred: score 0) (non-luminal: NLH). AR expression was assessed by immunostaining pre-neoadjuvant chemotherapy biopsy specimens, positive with Allred score >= 4. The pathological complete response, disease-free survival, and overall survival rates were compared between AR-positive and AR-negative groups. Results We classified 82 patients with HER2 + invasive BC into LH (n = 45, 54.9%) and NLH groups (n = 37, 45.1%), and AR + was observed in 43 patients (52.4%) (LH: 23, 51.1%; NLH: 20, 54.1%;p = 0.79). Quasi-pathological complete response was observed in 40 patients (48.8%) (LH: 18, 40%; NLH: 22, 59.5%;p = 0.08) overall, and in 31 AR + patients (72.1%) (LH: 15, 34.9%; NLH: 16, 37.2%), significantly higher than in the AR - group for both subgroups (p < 0.001). Regarding prognosis, disease-free survival was relatively better in the AR + group in all HER2 + BCs (p = 0.085), and overall survival was significantly better in the AR + group for NLH (p = 0.029). Conclusions High AR expression may be a useful predictor of therapeutic effects and prognosis in both subgroups of HER2 + BCs.