LONG-TERM HORMONE REPLACEMENT THERAPY AND RISK OF BREAST-CANCER IN POSTMENOPAUSAL WOMEN

Despite extensive study, concerns remain about a possible association between long-term postmenopausal hormone treatment-particularly use of combination preparations-and risk of breast cancer. The authors evalu ated the use of postmenopausal hormone replacement therapy in relation to breast cancer risk in a large multicenter, population-based case-c ontrol study. Women with a new diagnosis of breast cancer were identif ied through statewide tumor registries in Wisconsin, Massachusetts, Ma ine, and New Hampshire. Controls were randomly selected from populatio n lists in each state. For this analysis of postmenopausal women, data were available from 3,130 breast cancer cases and 3,698 controls inte rviewed between 1989 and 1991. Replacement hormone use was not associa ted with breast cancer risk in women who had ever undergone this treat ment (relative risk (RR) = 1.05, 95% confidence interval (CI) 0.93-1.1 8). Among women who had used replacement hormones for 15 years or more , there was no clear increase in risk, although the small sample size did not preclude the possibility of a modest association (RR = 1.11, 9 5% CI 0.87-1.43). Risk among women using progestins in combination wit h estrogens was similar to that in women using estrogens alone. Risk d id not vary according to type of menopause, family history of breast c ancer, history of benign breast disease, or alcohol intake. These resu lts are consistent with the majority of reports which find no overall increased risk associated with the use of replacement hormones. Howeve r, in contrast to several other studies, this study did not find long- term use to be associated with increased risk. These results also do n ot support a hypothesized effect of combined progestin and estrogen us e on the risk of breast cancer.