OESTROGEN RECEPTORS AND THE RESPONSE OF METASTATIC BREAST CANCER TO AMINOGLUTETHIMIDE OR TAMOXIFEN

Oestrogen receptor (ER) measurements in metastatic and primary tumours from patients with breast cancer have been correlated with the objective tumour response to treatment with aminoglutethimide (24 patients) or tamoxifen (39 patients). The rate of response in patients with ER-positive tumours (aminoglutethimide 69%, tamoxifen 70%) was significantly greater than in those with ER-negative tumours (aminoglutethimide 9%, tamoxifen 10%). Five of six patients showing an objective response to tamoxifen treatment responded later to aminoglutethimide, whereas only two of 12 patients who had not responded to tamoxifen responded later to aminoglutethimide. Toxicity rates were low for tamoxifen (5%), and reasonably low with aminoglutethimide (20%). Because of the low toxicity of tamoxifen, this agent could reasonably be used in breast cancer regardless of the availability of tumour ER measurements. The use of aminoglutethimide could be based either on the presence of ER in the tumour or on the response to previous tamoxifen therapy.