Estrogen receptor in breast cancer of the Japanese

The estrogen receptor was assayed, using the 2,000g supernatant and dextran-coated charcoal method, in 243 tissue samples from human breast cancer, benign breast diseases, macroscopically normal breast tissues, normal uterine myometrium, and uterine myoma. The estrogen receptor was found to be positive in 52.1% of 98 primary breast cancer and in 54.1% of 24 metastatic tumors. The receptor in the breast cancer was found to be similar to that in normal uterine myometrium in the binding character; that is, the dissociation constant of 10(-9) approximately 10(-11) M and number of binding sites of 0 approximately 2,800 fmol/mg protein. There was no correlation between the presence of the receptor and some clinical factors such as menopausal status, age of the patient, urinary 17-ketosteroid excretion, clinical stage of cancer, tumor size, positive or negative axillary lymph node metastasis, histological type, metastatic site of the cancer, or disease-free interval. The estrogen receptor appeared to be retained by metastasis of cancer, and this may lead to the use of the receptor assay with mastectomy specimens for the prediction of response to hormonal therapy in future recurrence of malignancy. Furthermore, it may be possible by this assay to select patients suitable for adjuvant therapy with hormones at the time of mastectomy. A good correlation was found between the presence of the receptor and response to the major endocrine ablation therapy in patients with advanced or metastatic breast cancer. When the receptor was negative in the cancer tissue, the change of response to the endocrine therapy was minimum. On the other hand, if the cancer contained the receptor, approximately 60% of the patients with metastatic or advanced breast cancer responded well to the major endocrine ablation therapy. Thus, the estrogen receptor of breast cancer in Japanese patients appears to bear a close resemblance to that reported in Western patients in its incidence and the correlation to some biological characteristics of the cancer.