An Association between Steroid Hormone Receptors and Response to Cytotoxic Chemotherapy in Patients with Metastatic Breast Cancer1

The relation between steroid hormone receptors and the response rate to cytotoxic chemotherapy in 70 pa tients with metastatic breast cancer was determined in a retrospective study. Thirty-four of 45 patients with low or absent estrogen receptor values had objective responses to chemotherapy, whereas only three of 25 patients with estrogen receptor-positive tumors responded (p < 0.0001). Furthermore, 22 of 34 patients with low or absent progesterone receptor tumors had an objective response to cytotoxic chemotherapy, while zero of eight patients with a positive progesterone receptor tumor responded (p < 0.01). Patients having tumors with a negative estrogen receptor and a negative progesterone receptor had a response rate of 21 of 24 (88%). This high response rate to chemotherapy in patients whose tumors lacked estrogen receptor or progesterone receptor could not be explained by differences between the two groups with respect to age, menopausa! status, disease-free interval, Karnofsky performance index, sites of involvement with metastatic tumor, extent of disease, or type of chemotherapy admin istered. Chemotherapy response was not associated with the presence or absence of either androgen or glucocorticoid receptor. We conclude that estrogen and progesterone receptor values are important predictors of response to cytotoxic chemotherapy in metastatic breast cancer.