Influence of estrogen receptor status on response of metastatic breast cancer to aminoglutethimide therapy

Aminoglutethimide (AG) is an effective chemical ablative form of therapy for metastatic breast cancer in postmenopausal women. Estrogen receptor (ER) status in breast cancer is useful in predicting the response to the hormonal treatments. Of 134 postmenopausal metastatic breast cancer patients treated with AG, ER analysis was done in 63 patients, 52 of whom are now evaluable. ER biopsy was performed prior to Ag therapy in 61 patients, but the results were not known to the investigators. ER value greater than or equal to 10 fmol/mg cytosol protein was considered ER positive (ER+), 4-9.9 fmol/mg borderline, and less than 4 fmol/mg ER negative (ER-). In 38 ER+ patients, objective response rate was 50% (three complete response, 16 partial response) and eight stabilization. Median duration of objective response was 15 months. Forty-three percent of the patients with borderline estrogen receptor level responded objectively (three partial response) with the median duration of response eleven months. Fourteen percent of ER- patients responded objectively (one complete response). Hence the estrogen receptor level predicts response in ER+ and ER borderline patients treated with AG.