The prognostic role of progesterone receptors in human breast cancer.

Estrogen-receptor protein is known to be an important prognostic factor for patients with breast cancer. The presence of estrogen receptor correlates with response to endocrine therapy in patients with metastatic disease and is associated with prolonged disease-free survival and overall survival in patients with primary disease. But the correlation between estrogen-receptor positivity and endocrine dependence is not perfect--approximately 40% of estrogen-receptor-positive tumors fail to regress with endocrine therapy. It has been hypothesized that another protein, progesterone receptor, may be a more effective marker of endocrine responsiveness since progesterone receptor is an end product of estrogen action. Promising retrospective results indicate the need for new, prospective clinical trials to define further the prognostic value of progesterone receptor for patients with advanced disease. For patients with primary breast cancer, we have found that progesterone receptor appears to be more important than estrogen receptor for predicting time to recurrence. We suggest that both estrogen receptor and progesterone receptor be routinely measured in all breast cancer tumors.