The identification of steroid receptors in human breast cancer tissues has provided biochemical markers to predict hormone responsiveness. Analysis of tumors from 328 patients for the estrogen receptor protein (ERP) revealed significant levels in 225 patients (68%). Fifty-five patients with advanced disease were subjected to hormonal manipulation. Thirty patients underwent ablative surgery consisting of adrenalectomy or adrenalectomy and oophorectomy. Twenty-five patients were treated with additive therapy utilizing the new antiestrogen Tamoxifen. The ECOG criteria for an objective response were applied to all patients. Fifteen of the 24 estrogen receptor-positive patients (63%) subjected to endocrine ablation responded. Eleven of twenty (55%) ERP-positive patients responded to Tamoxifen therapy. Only one ERP-negative patient responded in the total group. Simultaneous analysis of these same specimens for the progesterone receptor protein (PgRP) revealed that 151 patients were ERP and PgRP positive (46%); 74 (23%) were ERP positive and PgRP negative; 90 (27%) were ERP and PgRP negative, and 13 (4%) were ERP negative and PgRP positive. In the two treatment groups the overall response rate when both receptors were positive was 77% with a higher percentage of responders in the endocrine ablative group (88% vs. 64%). Ln addition, a greater duration of response was achieved in those patients treated with endocrine ablation.
Cancer 452992-2997, 1980.
ITHIN R E C ~N T YEARS increasing emphasis has been placed on the role of estrogen receptor proteins (ERP) in the management of patients with advanced breast cancer. Prior to the determination of this biochemical marker, clinical acumen could achieve only a 40% response rate to hormonal manipulation in patients with advanced disease. The results of findings presented in 1974 at the International Meeting of the Breast Cancer Task Force in Bethesda, Maryland, revealed approximately a 55% response rate to endocrine therapy in those women whose breast tumors contained significant levels of ERP, and less than 8% response rate in those women with ERP negative tumors." With the advent of improved methodologies for detecting ERP as well as improved criteria for defining critical levels of tumor receptor content in relation to clinical application, the ability to select