Steroid hormone receptors in breast cancer management

Estrogen and progesterone receptors (ER and PR) have now been studied in clinical breast cancer for more than 20 years. Positive receptor status correlates with favorable prognostic features including a lower rate of cell proliferation and histologic evidence of tumor differentiation. During the first several years after diagnosis, patients with ER-positive tumors tend to have a lower recurrence rate; however, this is balanced by a higher recurrence rate in subsequent years so that the overall prognostic significance of receptor status is modest. ER and PR have their greatest utility in predicting response to hormonal therapy, both in the adjuvant setting and for advanced disease. When the assay is done properly and cut-offs for ER-negativity and positivity are defined by clinical studies of patients treated with endocrine therapy, receptor status is very helpful in identifying groups of patients who are very unlikely to benefit from hormonal therapy. Tumors that express both ER and PR have the greatest benefit from hormonal therapy, but those containing only ER or only PR still have significant responses.