Prognostic factors in primary breast cancer.

Estrogen receptor (ER) has been well documented as an important predictor of long disease-free intervals and survival for patients with primary breast cancer (1). In advanced breast cancer it has been hypothesized that the presence of progesterone receptor (PR) might be a more sensitive marker for predicting response to endocrine therapy (2, 3). We have recently found that PR was more important than ER in predicting disease-free survival for a group of patients with stage-II breast disease that was treated according to a randomized protocol (Clark et al., submitted for publication). This report examines the generality of that result by extending our analysis to include patients from other institutions. The additional patients were not treated according to a rigid clinical protocol, but rather received treatments in much the same way as the majority of breast cancer patients in a community practice. Of interest was whether the relationship between steroid receptors and disease-free survival that we have previously reported would hold with this new group of patients with different demographic and treatment profiles. The relationships between steroid receptor levels and both disease-free and overall survival were examined in detail.