A case-control study of breast cancer stratified by estrogen receptor status.

A population-based case-control study was conducted to examine whether tumor estrogen receptor status differentiated risk factor patterns for breast cancer. From December 1980 to December 1982, 458 women with newly diagnosed breast cancer and 568 control women, aged 20-54 years, from the Atlanta, Georgia, metropolitan area were interviewed. On the basis of tumor estrogen receptor results, cases were classified as receptor-positive or receptor-negative. Intercase analysis showed that age was positively and significantly associated with estrogen receptor-positive breast cancer (p = 0.001); the relative risk for an estrogen receptor-positive as opposed to an estrogen receptor-negative tumor was elevated threefold among women aged 50-54 years compared with those aged less than 35 years. In the case-control analysis, race was the only individual factor that demonstrated a significant difference in the risk for estrogen receptor-positive versus estrogen receptor-negative cancer (p less than 0.05), with blacks being at a 25% excess risk for estrogen receptor-negative cancer compared with whites. Although a history of benign breast disease was a risk factor for both positive and negative tumors, the association was stronger for the estrogen receptor-positive tumors. Postmenopausal women were at a lower risk for both cancer subtypes compared with premenopausal women. Compared with non-users, women who had ever taken oral contraceptives had a 16% decrease in the risk for receptor-positive cancer and a 22% increase in the risk for receptor-negative cancer. These results are consistent with the notion that certain exposure variables may relate to hormonal status, possibly by augmentation or suppression of estrogen receptor activity.