Hormone replacement therapy and some risk factors for breast cancer among Slovenian postmenopausal women

Objective The aim of the study was to examine the influence of the use of hormone replacement therapy (HRT) and of some generally recognized risk factors on breast cancer risk among Slovenian postmenopausal women. Methods Eligible women diagnosed with breast cancer and a control group of women of the same age and ethnicity were invited to participate in the case-control study via a personal letter and asked to complete a written questionnaire. Adjusted odds ratios and 95% confidence intervals were estimated using multivariate logistic regression analysis. Results A total of 784 cases and 709 controls aged 50-69 years were enrolled. HRT use was inversely associated with breast cancer risk. The effect was most pronounced with the use of estrogen-only replacement therapy (odds ratio (OR) 0.51, 95% confidence interval (CI) 0.30-0.87). Longer duration of HRT use did not result in a significant change in risk (1 to <5 years of HRT use: OR 0.44, 95% CI 0.26-0.73; >= 5 years of HRT use: OR 0.51, 95% CI 0.30-0.87). Obesity (25 <= body mass index <30 kg/m(2) : OR 1.34, 95% CI 1.04-1.73; body mass index >= 30 kg/m(2) : OR 1.89, 95% CI 1.36-2.63), smoking >= 10 cigarettes per day (OR 1.70, 95% CI 1.20-2.43), and any first-degree relative with breast or ovarian cancer (OR 1.52, 95% CI 1.11-2.08) were positively associated with breast cancer risk. Conclusions Our analysis revealed some differences from the previously published literature, which might reflect underlying demographic changes. Comprehensive medical care in HRT users without pre-existing breast abnormalities probably reduces the incidence of new breast cancer cases in Slovenia.