The use of steroïd hormone receptors in the treatment of human breast cancer: a review.

Basic research into the mechanisms of steroid hormone action in breast cancer has led to significant advances in our understanding and treatment of this disease. The hypothesis that measurement of estrogen receptor (ER) in breast cancer tissue might be useful in predicting the endocrine dependence of a tumor has been proven to be correct. The absence of ER connotes hormone independence and precludes a trial of endocrine therapy. Tumors selected for hormonal treatment on the basis of a positive ER respond to endocrine therapy at nearly twice the rate of those chosen by clinical criteria alone. However, a third of ER positive tumors fail to respond. Recently, research has been directed toward increasing the accuracy of the assay in the ER positive group. The concentration of ER in the tumor and the measurement of progesterone receptor (PgR) appear to improve the predictive accuracy of the test. The ER status of primary breast cancer is also a marker for the length of time to recurrence after mastectomy and for ultimate patient survival. Thus, in addition to its importance in the selection of treatment for advanced disease, the ER assay may also prove valuable in planning new adjuvant treatment strategies.