Estrogen receptor beta expression in invasive breast cancer

The aim of this work was to determine the extent of estrogen receptor beta (ER-beta) expression in invasive breast cancer (BrCA) and whether ER-beta e xpression is correlated with response to adjuvant hormonal therapy with tam oxifen (AHTT). Immunohistochemical staining (IHC) for estrogen receptor alp ha (ER-alpha) and ER-beta was performed on sections of formalin-fixed and p araffin-embedded tissue from 47 unselected invasive breast carcinomas (BrCA ). IHC for ER-beta was also performed on sections of BrCA from 118 women wh o were treated with mastectomy and AHTT. Survival analysis was performed us ing the Kaplan-Meier method and the log-rank test. Of the 47 unselected BrC A, 17 (36%) were negative for ER-alpha and of these, 8 (47% of ER-alpha neg ative cases and 17% of all 47 patients) were ER-beta positive. Five of the 8 ER-alpha negative and ER-beta positive cases were positive for ER biochem ically. There was no correlation between ER-beta positivity and overall sur vival in the unselected group. By contrast, in the group of women treated w ith AHTT, expression of ER-beta in more than 10% of cancer cells was associ ated with better survival (P = .0077), even in women with node-negative BrC A (P = .0069). In conclusion, our results show that a significant number of women with BrCA are positive for ER-beta only, and may be determined to be ER-negative when currently available IHC is used. ER-beta status is a sign ificant predictor of response to AHTT in women with BrCA Larger studies wit h multivariate analysis are needed to confirm these findings. Copyright (C) 2001 by W.B. Saunders Company.