Clinicopathological importance of estrogen receptor-β in breast cancer of Japanese women

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PURPOSE. The clinicopathological importance of a second estrogen receptor, ER-β, in breast cancers has been intensely studied; however, there is still no real consensus regarding the clinical utility of an ER-β assay, probably because of the lack of standardized methodology, the presence of several ER-β isotypes (ER-β1-5, etc.) and, more importantly, the lack of convincing data on whether an ER-β status provides clinically useful information over what is already provided by the traditional estrogen receptor (ER-α)/progesterone receptor (PR) assay. A large and systematic study is needed to address these important issues.MATERIALS AND METHODS. Archival materials of 442 invasive breast cancers from women treated with adjuvant tamoxifen monotherapy and a long follow-up period (median 11.1 years) were subjected to immunohistochemical study using four commercially available anti-ER-β antibodies; anti-ER-β1 monoclonal, anti-ER-βcx (= ER-β2) monoclonal, anti-ER-β1-3 monoclonal, and anti-ER-β1-3 polyclonal.RESULTS. ER-β expression correlated with a favorable prognosis regardless of the antibody, although anti-ER-β1 monoclonal antibody appeared to be the best marker. In multivariate analysis, ER-β1 status emerged as an independent prognostic factor. ER-β1 status was a significant predictor of survival in postmenopausal, but not premenopausal, women. Prognostic value of ER-β1 is especially distinct among patients with ER-α-negative/PR-negative or ER-α-negative/PR-negative/HER2-negative tumors, a group of patients widely believed to be hormone unresponsive, have poor prognosis, and needing chemotherapy.CONCLUSION. Immunohistochemical examination of ER-β1 in addition to ER-α and PR is clinically important to predict survival of patients with breast cancer treated with tamoxifen monotherapy. ER-β1 examination may optimize breast cancer treatment.