Hormone dependency of breast cancer.

Quantitative determination of the estrogen receptor (estrophilin) content of an excised tumor specimen provides information useful in selecting the type of systemic therapy best suited to the individual patient with advanced breast cancer. Women whose tumors contain low or negligible amounts of estrophilin rarely respond to endocrine ablation or other hormone therapy, whereas most but not all patients with receptor-rich cancers receive benefit from endocrine treatment. Properly interpreted, estrophilin assay predicts hormone dependency correctly in 85 to 90 percent of the cases. Analysis of the primary tumor at the time of mastectomy not only serves as a guide to subsequent therapy if metastases should appear but it also provides a clue to the probability and rapidity of recurrence. Because present methods for receptor determination have certain limitations, we are developing an immunoassay, based on monoclonal antibodies to human estrophilin, that promises to provide a simple, inexpensive procedure for the routine analysis of breast cancer specimens.