[Experimental study on the determination of estrogen receptor and the effect of antiestrogen therapy in breast cancer].

Thirty-five patients with breast cancer were examined for estrogen receptor (ER) by biochemically and immunohistochemically, and sensitivity to antiestrogen agents was investigated experimentally in order to obtain strict indications for antiestrogen therapy. Biochemically, cytoplasmic and nuclear ER (ERc and ERn) were determined using the DCC method. Immunohistochemical assay of ER (ER-ICA) was carried out using the enzyme-labeled antibody method. Sensitivity to antiestrogen agents was determined by subrenal capsule assay (SRCA). 1. The positive rates were 63.0% for ERc, 40.7% for ERn, and 44.4% for ER-ICA. 2. Anti-estrogen therapy was effective in 64.7% of ERc-positive patients, 72.7% of ERn-positive patients, and 91.7% of ER-ICA-positive patients. 3. ER-ICA was negative in 83.3% of ERc-positive patients who did not respond to antiestrogen therapy. Both of the two patients who were negative for ERc and responded to antiestrogen therapy were ER-ICA-positive. Thus, it seems possible that indications for antiestrogen therapy can be specified more strictly than before, using the results of ER assay by the enzyme-labeled antibody method.