Estrogen replacement therapy in women with a history of proliferative breast disease

BACKGROUND, Little information is available regarding the invasive breast c arcinoma risk associated with estrogen replacement therapy (ERT) in women w ith histories of histologically defined breast lesions. METHODS. A retrospective cohort study of a consecutive series of women who underwent breast biopsies that proved to be benign between 1952-1978 was co nducted. Follow-up data were obtained for 9494 women (87.6% of women eligib le for follow-up). To investigate the effect of ERT on invasive breast carc inoma risk, the analysis was restricted to women with premenopausal breast disease whose follow-up extended through menopause and who did not develop premenopausal breast carcinoma. Relative risks were calculated with respect to women who took ERT but whose benign breast biopsies had neither atypica l hyperplasia (AH), complex fibroadenoma (CFA), nor proliferative disease w ithout atypia (PDWA). RESULTS. During 190,845 woman-years of follow-up there were 444 confirmed c ases of invasive breast carcinoma in the entire cohort. Women with a histor y of AH had relative risks of invasive breast carcinoma of 2.87 (95% confid ence interval [95% CI], 1.3-6.3) and 2.53 (95% CI, 1.0-6.3) if they did or did not take ERT, respectively. For women with a history of CFA these risks were 1.57 (95% CI, 0.72-3.4) and 1.46 (95% CI, 0.53-4.0), respectively, wh ereas for women with a history of PDWA they were 1.37 (95% CI, 0.88-2.1) an d 1.13 (95% CI, 0.69-1.9), respectively. CONCLUSIONS. ERT does not significantly elevate the risk of invasive breast carcinoma in women with previous histologically defined benign breast dise ase. Therefore, ERT is not contraindicated in these women. Cancer 1999;85:1 277-83. (C) 1999 American Cancer Society.