HORMONE REPLACEMENT THERAPY AND RISK OF BREAST-CANCER - RESULTS FROM EPIDEMIOLOGIC STUDIES

OBJECTIVE: We combined data from published reports of the relation bet ween estrogen use and breast cancer. We specifically addressed the hyp othesis that the addition of progestins to estrogen therapy reduces th e risk of breast cancer.STUDY DESIGN: A meta-analysis was performed. R ESULTS: Replacement hormone therapy is not associated with increased r isk of breast cancer in women who have ever used it (relative risk 1.0 2, 95% confidence interval 0.93 to 1. 1 2). However, current use is as sociated with increased risk (relative risk 1.40, 95% confidence inter val 1.20 to 1.63). Although there was no significant trend with increa sing duration of use, women with greater-than-or-equal-to 10 years of estrogen use had a relative risk of 1.23 (95% confidence interval 1.08 to 1.40). However, data on use of estrogen plus progestins combined f rom four studies indicate that risk is not reduced and that the overal l relative risk is 1.13 (95% confidence interval 0.78 to 1.64). Furthe r, risk did not vary in strata of family history or benign breast dise ase. CONCLUSION: Although these results exclude a large effect of horm one therapy on risk of breast cancer, we are unable to rule out some r isk associated with current or long-term estrogen use.