Prognostic Significance of High Expression of ER-beta in Surgically Treated ER-Positive Breast Cancer Following Endocrine Therapy

PURPOSE: This study evaluated estrogen receptor (ER)-beta mRNA and ER-beta protein expression and its prognostic implications in hormone receptor-positive breast cancer. METHODS: Paraffin sections from 139 hormone receptor-positive breast cancer cases were prepared. The expression of ER-beta mRNA and protein were analyzed by branched-chain assay and immunohistochemistry (IHC), respectively. RESULTS: The Allred score of ER-beta IHC was correlated with smaller tumor size (p=0.043), the Allred score of ER-alpha IHC (p<0.001), and the Allred score of progesterone receptor (PR) IHC (p=0.022) but not with the HER2 IHC score. ER-beta mRNA level was correlated with PR mRNA levels (p<0.001) but not with the Allred score of ER-beta IHC, ER-alpha IHC, and PR IHC, nor with the HER2 IHC score and ER-alpha mRNA level. In survival analysis, high expression of ER-beta mRNA was associated with worse disease-free survival along with poor differentiation, lymph node metastasis and absence of PR protein expression in univariate analysis (p=0.040, p=0.002, p=0.018, and p=0.007, respectively) and multivariate analysis (p=0.044, p=0.002, p=0.035, and p=0.007, respectively). CONCLUSION: High expression of ER-beta mRNA is an independent predictor of disease recurrence in hormone-receptor-positive breast cancer.