The influence of obesity and age at diagnosis on the estrogen receptor status of breast cancers. Perimenopausal predominance of estrogen receptor negative tumors.

Estrogen receptor (ER) status of 763 primary breast cancers was analyzed by host age and obesity. Tumors from women less than 40 years of age were found to be ER negative (ERN) predominantly. Tumors from women greater than 40 years of age demonstrated increasingly higher median values for ER protein and were ER positive (ERP) predominantly except for those presenting among nonobese women 45 to 49 years of age and obese women 50 to 54 years of age. Tumors from these two subgroups were more frequently ERN than those from women of similar habitus who were immediately younger (P less than 0.05) or older (P less than 0.02), or than those from women of the same age and differing obesity status (45 to 49 years of age P less than 0.01; 50 to 54 years of age P greater than 0.05). This altered pattern of estrogen binding in perimenopausal tumors likely results from the hormonal changes of the menopausal and late premenopausal years. Recognition of their varied patterns of estrogen binding should assist in understanding the behavior of these perimenopausal tumors and in the selection of optimal antitumor therapy for their hosts.