IMMUNOHISTOCHEMICAL DETECTION OF HORMONE RECEPTORS IN BREAST CARCINOMAS (ER-ICA, PGR-ICA) - PROGNOSTIC USEFULNESS AND COMPARISON WITH THE BIOCHEMICAL RADIOACTIVE-LIGAND-BINDING ASSAY (DCC)

In a prospective study conducted since 1983, the hormone-receptor status of primary breast carcinomas was investigated using immunohistochemical (ER-ICA, PgR-ICA) and biochemical (DCC) methods. The degree of immunohistochemical staining was evaluated according to the immunoreactive score (IRS) devised by Remmele and Stegner [Frauenarzt 28, 41-43 (1987)]. The findings obtained using the biochemical radioactive-ligand-binding assay (cutoff level, 20 fmol/mg) and those obtained using qualitative immunohistochemical methods were in agreement in 72.5% (ER-ICA) and 72.2% (PgR-ICA) of cases. For the 789 cases of primary breast carcinoma examined, postoperative data were available for a mean follow-up period of 48 months. Using the statistical procedure of Kaplan-Meyer to analyze the probability of disease-free and overall survival, it emerged that ER-ICA- and PgR-ICA-positive breast carcinomas exhibited the most favorable course of disease. Breast carcinomas with negative immunohistochemical findings for both types of receptor were found to have a significantly less favorable disease course. Semiquantitative evaluations of the staining results using the IRS failed to yield significant differences among the 12 IRS groups. Neither the percentage of positive tumor cells nor the immunohistochemical staining intensity proved to be prognostically useful parameters for predicting the course of disease. In comparison to the established biochemical method for the demonstration of hormone receptors, however, the immunohistochemical procedure was found to be superior with respect to prognostic meaningfulness, particularly in the group with conflicting biochemical and immunohistochemical findings with respect to hormone-receptor status. Using Cox analysis, the prognostic usefulness of the immunohistochemical test was compared with that of certain established prognosis parameters (pT, pN, grading, Ki-67), from which it became apparent that PgR-ICA has the greatest prognostic value, with the most lasting influence on the course of disease. The results of the present study demonstrate that, with respect to the prognostic value of its findings, the immunohistochemical test for hormone receptors is superior to the biochemical procedure. (C) 1994 Academic Press, Inc.