[Determination of estrogen receptors in 160 breast tumors using monoclonal antibodies: comparison of Abbott's immunoenzymatic method with the carbon dextran method].

Estrogen receptor determinations were performed on 241 cytosols from 160 breast cancer tumors, using both dextran coated charcoal method (D.C.C.) and monoclonal antibodies (Abbott's ER-EIA kit) in order to compare the two methods, and to evaluate the clinical usefulness of this new immunological simplified assay. Intra- and inter-assay reproducibility were studied during a six month period. Intra-assay of both methods were lower than 5%. Inter-assay variation coefficients of ER-EIA studied on 35 standard curves varied from 12.5% (standard: 0) to 6.7% (standard: 250 fmoles/ml). ER determination of 80 human breast cancers were performed both by EIA and Scatchard analysis. The regression curve obtained was (EIA) = 1.04 (Scatchard) + 21 fmoles/mg of proteins (r = 0.963). With 153 breast cancer cytosols whose volume was too small for multipoint Scatchard analysis, EIA results were compared to results obtained by a "near saturating" concentration of tritiated ligand (5 nM). The regression curve obtained was (EIA) = 1.34 (5nM) + 5 fmoles/mg proteins (r = 0.978). These results can be compared with those obtained between Scatchard and 5 nM: (Scatchard) = 1.29 (5nM) - 9 fmoles/mg proteins (r = 0.985). Reproducibility was studied on clinical specimens assayed at two different periods during the clinical evaluation. Regression curves obtained were (2nd assay) = 1.05 (1st assay) - 5.5 fmoles/mg proteins for EIA, and (2nd assay) = 0.96 (1st assay) + 9 fmoles/mg proteins for DCC method. EIA assay presented an high stability for protein concentrations very low, up to 0.2 mg/ml. Finally, a very good correlation was obtained between ER-EIA and DCC method, and ER-EIA seemed specially well fitted to small tumors.