Risk of breast cancer associated with the use of hormone therapy. Retrospective analysis using a logistic regression model

Background: Breast cancer (BC) is the most common cancer among women and a significant global health problem. Several genetic, external and environmental risk factors have been reported, including the use of oral contraceptives and hormone replacement therapy. The aim of this study was to obtain data on the BC risk of women residing in the Northeast of Italy comparing women who take hormone therapy with those who do not. Patients and Methods: We retrospectively reviewed data regarding a series of 404 consecutive women (median age 57 years, range 26-89 years) who underwent curative surgery for primary breast cancer (pT1a=3.7%, pT1b=17.3%, pT1c=35.4%, pT2=36.6%, pT3=7.0%), and 407 health controls. Age, family history of BC, data concerning the reproductive life, smoking, alcohol abuse, physical activity, hormone therapy administration, and body mass index (BMI) were considered as factors in a multivariate logistic regression model used to estimate odds ratios (OR) and 95% confidence interval (CI). Results: Age >50 years (OR=2.0, 95% CI 1.4-2.8), history of BC in mother or sisters (OR=3.5, 95% CI 1.7-6.9), early (<12 years) menarche (OR=2.1, 95% CI 1.5-3.0), late (>30 years) age at first birth (OR=2.5, 95% CI 1.2-5.2), use of oral contraceptives (OR=1.8, 95% CI 1.2-2.6), hormonal replacement therapy (OR=1.6, 95% CI 1.1-2.3), and BMI>24 (OR=1.8, 95% CI 1.3-2.5) were associated with an increased risk of BC, whilst the risk decreased with breastfeeding (OR=0.4, 95% CI 0.3-0.5). The duration of estrogen replacement therapy was significantly (p<0.01) different between cases and controls (43.7±30.2 vs. 30.6±23.3 months). Conclusions: Several parameters traditionally considered in epidemiological studies did not result useful as RF suggesting that environmental and external factors should be considered to correctly select high risk population. Moreover, the use of both oral contraceptives and hormone replacement therapy did not represent strong RFs in patients with BC.