Clinical usefulness of estrogen receptor immunocytochemistry in human breast cancer

We assessed the reliability of the immunocytochemical assay of estrogen receptor (ER-ICA) as a marker of clinical outcome. Relapse-free interval (RFI) and overall survival (OS) according to ER-ICA status were retrospectively evaluated on a series of 210 patients who had undergone surgery for primary breast cancer between January 1985 and December 1988. ER assay by the dextran-coated charcoal method (DCC) was also performed in 189 tumors. A significant positive correlation was found between the DCC and ER-ICA assays, with an overall agreement of 79%. ER-ICA status showed a prognostic predictive power with respect to OS and RFI in the whole series of patients and in the subset of node-positive patients. It was also a marker of outcome with respect to OS in the subsets of node-negative patients and patients with tumors < or = 2 cm in diameter. Moreover, the predictive value of the ER-ICA assay was higher than that of the DCC assay in the present study. These findings emphasize the clinical usefulness of the ER-ICA assay as a measure for prognosis.