Hormone replacement therapy and risk of benign proliferative epithelial disorders of the breast

Use of hormone replacement therapy (HRT) has been associated with increased risk of breast cancer, and it is possible that this reflects a positive as sociation between HRT use and risk of proliferative forms of benign breast disease (BBD), conditions which are thought to have pre-malignant potential . The purpose of the present investigation was to study the association bet ween HRT use and risk of benign proliferative epithelial disorders of the b reast (BPED). The study was undertaken using the 56,837 women within the Ca nadian National Breast Screening Study (NBSS) who completed self-administer ed lifestyle and dietary questionnaires. (The NBSS is a randomized controll ed trial of screening for breast cancer in women aged 40-59 at recruitment. ) During the course of the follow-up period, a total of 691 women in the di etary cohort were diagnosed with biopsy-confirmed incident BPED. For compar ative purposes, a sub-cohort consisting of a random sample of 5681 women (i ncluding 65 of the subjects with BPED) was selected from the full dietary c ohort. After exclusions for various reasons, the analyses were based on 691 cases and 5443 nan-cases. In postmenopausal women, in whom most of the rep orted use occurred, there was a positive association between duration of HR T use and risk of BPED, the adjusted incidence rate ratio (95% confidence i nterval) in those who had used HRT for more than 8 years being 1.70 (1.06-2 .72). There were too few cases of atypical BPED for meaningful analysis, bu t results for those whose BPED showed no atypia were similar to the overall results. Further analyses conducted separately in the screened and control arms of the NBSS were similar to those observed overall, as were those con ducted separately for screen-detected and interval-detected BPED. (C) 1999 Lippincott Williams & Wilkins.