Estrogen and progesterone receptors in the prediction of response of breast cancer to endocrine therapy.

This review presents our experience with the use of estrogen receptors (ER) and progesterone receptors (PgR) in the prediction of response to endocrine therapy in stage IV breast cancer. Presence of ER (> 3 fmol/mg cytosol protein) significantly predicted response to the antiestrogen tamoxifen and to hypophysectomy. ER-negative patients did not respond to either modality of therapy in our series. The absolute amount of ER did not significantly improve our ability to predict response to hormone treatment. In our experience, limited to a small number of patients, the presence of PgR in addition to ER did not increase the probability of response to endocrine therapy. Our findings underscore the usefulness of ER measurement in the prediction of response to either antiestrogen therapy or hypophysectomy in metastatic breast cancer.