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April 10, 1991

Estrogen Replacement Therapy and Risk of Breast Cancer

Author Affiliations

American Medical Association Chicago, Ill

American Medical Association Chicago, Ill

JAMA. 1991;265(14):1824-1825. doi:10.1001/jama.1991.03460140052014

To the Editor.—  Colditz et al1 categorized estrogen exposure into three groups: never users, current users, and past users. Past users are further stratified on duration of use and years since last use, and current users on duration of use. Based on these measures of estrogen exposure, the investigators note that "the past users of replacement estrogen were not at an increased risk [of breast cancer]..., including even those with more than 10 years of use (relative risk [RR] after adjustment for established risk factors, 0.70; 95% confidence interval [CI], 0.45 to 1.10)." This adjusted RR of 0.70 for past users with 10 or more years of use, however, appears to be inconsistent with data presented in Table 3 of the article by Colditz et al, in which the 0.70 RR refers to the adjusted RR for past users who stopped using estrogen 10 or more years ago. The