Impact of Nuclear Oestrogen Receptor Beta Expression in Breast Cancer Patients Undergoing Neoadjuvant Chemotherapy.

Introduction Oestrogen receptor beta (ER-beta) is abundantly expressed in breast cancer (BC), but its impact on neoadjuvant chemotherapy outcome is unknown. Patients and Methods Patients treated in the neoadjuvant GeparTrio trial with available tissue for immunohistochemical analyses were included. Nuclear ER-beta expression was correlated with clinico-pathologic characteristics. The impact of its expression on pathological complete response (pCR [ypT0/ypN0]) and survival was determined. Results Samples of 570 patients were available. Low nuclear ER-beta expression (IRS < 9) was observed in 48.4% of hormone receptor positive and 58.6% of hormone receptor negative tumours. Low nuclear ER-beta expression was associated with higher pCR rates compared to high nuclear ER-beta expression (16.1% vs. 4.7%, p = 0.026). Low ER-beta expression was no independent predictor of pCR in multivariate analyses. Diseasefree and overall survival were not statistically different between patients with high and low nuclear ER-beta expression. Triple-negative BCs showed low nuclear ER-beta expression in 57.7%, and pCR rates were 27.1% and 0% (p = 0.23) in low and high ER-beta expressing tumours, respectively. Conclusion Low ER-beta expression is associated with improved pCR rates in univariate analyses. However multivariate analyses and survival analyses do not indicate an impact of ER-beta on survival in patients undergoing neoadjuvant chemotherapy. Further examination of ER-beta as predictor for endocrine therapy might be of value.