COMPARISON OF ESTROGEN-RECEPTOR DETERMINATIONS BY A BIOCHEMICAL LIGAND-BINDING ASSAY AND IMMUNOHISTOCHEMICAL STAINING WITH MONOCLONAL-ANTIBODY ER1D5 IN FEMALES WITH LYMPH-NODE POSITIVE BREAST-CARCINOMA ENTEREDON 2 PROSPECTIVE CLINICAL-TRIALS

BACKGROUND. The measurement of estrogen receptors (ER) in breast cance r specimens has traditionally been assessed with a dextran-coated char coal assay (DCCA). More recently the immunohistochemical staining (IHC ) method has gained increasing popularity because of its ability to us e fixed tissue, assess needle biopsies, and reduce cost. Controversy e xists over the accuracy of IHC compared with that of DCCA in determini ng ER. We compared these two techniques using tumor tissue obtained fr om a large group of females with lymph node positive breast carcinoma with long term follow-up. METHODS. Breast carcinoma tissue was obtaine d from a large group of females with node positive breast carcinoma pa rticipating in two adjuvant chemotherapy trials. ER was determined by the traditional DCCA method and by IHC using the ER1D5 antibody. Disea se free survival (DFS) and overall survival (OS) were assessed by each of these methods. RESULTS. ER status was determined by DCCA and IHC i n tumor tissue obtained from 316 females. A concordance of 79% was obs erved for the determination of ER-positive tumors. Of the discordant r esults, the majority of DCCA-negative, IHC-positive tumors could be ex plained by a low level of DCCA positivity (<10 fmol) or IHC staining o f nonmalignant cells. A much higher rate of discordant results was obs erved in premenopausal females. Of the DCCA-negative, IHC-positive pat ients 97% were premenopausal and of the DCCA-positive, IHC-negative pa tients 79% were premenopausal. ER by DCC appears to perform better tha n ER by IHC as a prognostic factor in terms of DFS and OS. CONCLUSIONS . When compared with DCCA, IHC with monoclonal antibody ER1D5 appears to be a reasonable substitute for the determination of ERI Although DC CA appeared to perform better as a determinant of prognosis, ER detect ion is used primarily for deciding on hormonal therapy. Review of disc ordant cases indicates IHC may more accurately reflect the ER status o f malignant cells in some patients. Attention must be paid to quality control considerations in performance of IHC staining. (C) 1996 Americ an Cancer Society.