The Clinical Significance of the Estrogen Receptor β Expression for Endocrine Therapy in Patients with ERα-negative and Progesterone Receptor-positive Breast Carcinoma

target in breast cancer. ERβhas recently been identified to be distinct from ERα. In contrast to ERα, the functions of ERβin breast cancer are still unclear. We sought to determine whether the expression of ERβcan be used as a predictive marker for endocrine therapy for patients with ERαnegative breast cancer. Methods: Formalin-fixed, paraffinembedded tumor specimens from 52 patients with ER-/PR+ invasive breast cancer were immunostained for their ERβ expression. These patients were treated with adjuvant tamoxifen. The results were correlated with various clinicopathological variables and the follow-up data. The expressions of p53 and HER-2/neu were also analyzed and correlated with the ERβstatus. Results: An ERβexpression was observed in 53.8% (28/52) of the breast cancer samples. There was no correlation between the ERβexpression and the other clinicopathologic factors (age, tumor size, histologic type, nodal status, histological grade, stage, therapeutic modality, progesterone receptor (PR) expression, p53 expression and HER-2/neu expression). Recurrence was present in 7.7% (2/26) of the patients whose tumors had an ERβexpression, as compared to the presence of recurrence in 36.4% (8/22) of the patients whose tumors had no ERβexpression (p< 0.05). The patients with ERβnegative-tumors revealed lower disease free survival rate than those with ERβpositive-tumors (p<0.05). Of the 52 patients, 10 (19.2%) were p53 positive, and 11 (21.2%) were HER-2/neu positive. No significant correlations were observed between ERβand p53 or HER-2/ neu. Conclusion: These results suggest that ERβmight be a predictive marker of a response to endocrine therapy in patients with ER-/PR+ invasive breast cancer, although this needs to be confirmed by additional studies.