Postmenopausal hormone therapy and ductal carcinoma in situ: a population-based case-control study

Background and aim: The relationship between hormone therapy (HT) and invasive breast cancer has been extensively investigated, but the relationship between HT and in situ breast cancer has received relatively little attention. We examined the relationship between HT and ductal carcinoma in situ (DCIS) among postmenopausal women who participated in a population-based case–control study in Connecticut, USA. Methods: This analysis included 1179 post-menopausal women (603 controls and 576 cases), who comprised a subset of a population-based case–control study that included all incident cases of breast carcinoma in situ (BCIS) in Connecticut and frequency-matched controls by 5-year age intervals. Results: We found no association between DCIS and ever use of any HT (adjusted odds ratio (OR) = 0.85, 95% confidence interval (CI): 0.65–1.11); of estrogen alone (adjusted OR = 0.93; 95% CI: 0.68–1.29) or of estrogen and progesterone (adjusted OR = 0.75; 95% CI: 0.52–1.08). There was also no association between DCIS and current use of these hormones. In addition, estimated risk of DCIS did not increase with duration of use of these preparations. Conclusions: These results add to a small literature that remains inconclusive. To determine whether HT poses risk of in situ breast cancer, larger studies with greater power and precise control of important covariates (e.g., mammography screening) are needed, as are meta-analyses of available data.