Estrogen receptors in mammary cancer: correlation with age, menopausal status, and response to therapy.

The concentration of estrogen receptor protein (ER) in 113 primary or metastatic breast cancers was studied. ER was found to be correlated with the age of the patient. The ER values were generally lower in premenopausal patients (5.6 fmol/mg cytosol protein) than in postmenopausal patients (32.8 fmol/mg cytosol protein). The ER values of perimenopausal patients (0-5 years since the last menstrual period) were heterogeneous but generally closer to those of the premenopausal patients. Use of the ER determination for allocation of the patients either to hormonal (tamoxifen or nandrolonedecanoate) or to cytostatic (adriamycin-cyclophosphamide or Cooper's regimen) therapy was shown to result in highly satisfactory clinical response rates (including complete and partial remissions and stabilized disease) of 68% and 67%, respectively. The practical limit of ER concentration for selection is between 3 and 10 fmol/mg cytosol protein in breast cancer.