Effect of Adjuvant Therapy in Primary Breast Cancer in Relation to the Estrogen Receptor Level

Abstract

It has repeatedly been shown that the presence of estrogen receptors (ER) in breast cancer tissue is a predictor of the response to endocrine therapy [1–3]; in this respect the quantity of ER is more predictive than simple qualitative classification [2–4]. Little ER in the tumor also predicts an early recurrence of the disease [5, 6]. Consequently adjuvant endocrine manipulations after surgery might be expected to affect short-term recurrence rate only slightly, since the tumors that are the most likely to recur early, i.e., the receptor-poor cancers, are the least likely to be affected by the treatment. In contrast to this expectation, our previous report [7] and that of others [8] have demonstrated that adjuvant tamoxifen therapy results in an increased disease-free survival. We now further detail the results of a prospective trial of tamoxifen treatment for 2 years after surgery. The recurrence rates are correlated to the ER levels in the tumors.