Abstract
Estrogen receptors have been assayed in a series of primary breast cancers from postmenopausal women; 59% of which were estrogen-receptor positive. These patients survived for a significantly longer period of time than those whose tumors were estrogen-receptor negative. The effect of estrogen-receptor status was only seen (and then markedly accentuated) in patients who had lymph-node invasion at the time of mastectomy. Such determinations also appear to be of value in preselecting those patients who, on recurrence, will benefit from tamoxifen therapy.