[Inconsistency in quantitation of estrogen receptor and progesterone receptor with dextran charcoal method and enzyme...

Six hundred and eighty-eight breast specimens including 442 breast cancers were studied to investigate the consistency and correlations between dextran charcoal assay (DCC) and enzyme immunoassay (EIA) for estrogen receptor (ER) and progesterone receptor (PgR). In DCC, ER was quantitated with competition of 16 alpha-125I-estradiol and diethyl stilbesterol, and PgR with 3H-R5020 and R5020. In EIA, kit from Abbott was used in ER and PgR quantitation. The mean age of the patients was 52 years and the mean age of patients with benign lesions was 39 years. The consistency rate was 95% for ER, and 83% for PgR, while the consistency coefficient kappa was 0.90 and 0.66, respectively. For the specimens in which the number of binding sites was calculated in both DCC (x) and EIA (y), the correlation coefficient was 0.787 and the linear regression formula was y = 0.5x + 58. For PgR, the correlation coefficient kappa was 0.612 and the regression formula was y = 2.6x + 91. In multiple regression analysis for consistency of DCC and EIA, for ER, there was an inconsistent trend for positive PgR and a consistent trend for patients in their fifties. For PgR, the trend was inconsistent for benign lesions and positive ER. In comparison with the efficacy of endocrine treatment, no responder was found in ER negative patients for both DCC and EIA. In PgR-negative patients a responder was found for both DCC and EIA. By Western blot analysis, anti-ER antibody provided in the ER.EIA kit showed affinity only for ER alpha and not for beta. In conclusion, in terms of the treatment efficacy for both ER and PgR, the current use of ER with EIA instead of DCC seems to give equivalent result, and old DCC data can be converted into the regression formula. However, PgR calculated by EIA was not equivalent with that of DCC.