Risk of Breast Cancer in Relation to Combined Effects of Hormone Therapy, Body Mass Index, and Alcohol Use, by Hormone-receptor Status
A partir des données de deux cohortes danoises incluant 30 789 femmes âgées de plus de 50 ans, cette étude évalue l'association entre l'utilisation d'un traitement hormonal substitutif de la ménopause, l'indice de masse corporelle, une consommation d'alcool et le risque de cancer du sein, en fonction du statut des récepteurs hormonaux
Background: Alcohol consumption, increased body mass index (BMI), and hormone therapy are risk factors for postmenopausal breast cancer, but their combined effects are not well understood. Because hormone therapy is effective for the relief of menopausal symptoms, the identification of "high-risk" users is important for therapeutic reasons. We investigated interactions between hormone therapy use and alcohol-use/high BMI status in relation to invasive breast cancer risk, both overall and according to estrogen receptor (ER) status. Methods: Two Danish prospective cohorts were pooled, including 30,789 women aged 50+ years (study period 1981 to 2009). Information on risk factors was obtained in baseline questionnaires. We performed analyses using the Aalen additive hazards model. Serum estradiol and testosterone measurements were obtained in a subsample of approximately 1000 women. Results: During 392,938 person-years of follow-up, 1579 women developed invasive breast cancer. Among nonusers of hormone therapy, the risk of breast cancer was slightly increased with overweight/obesity and increasing alcohol consumption. Compared with normal-weight nonusers, the risk of breast cancer was higher in hormone therapy users across all BMI strata (P for interaction = 0.003). A markedly higher risk of breast cancer was also observed for alcohol combined with hormone therapy use compared with abstinent nonusers (P for interaction = 0.02). These effects were primarily restricted to ER-positive cases. Combined effects of hormone therapy/high BMI and hormone therapy/alcohol on serum estradiol and testosterone supported the hypothesis of a hormonal pathway linking these exposures to breast cancer. Conclusion: These analyses suggest an increased risk of breast cancer associated with hormone therapy use-a risk that may be particularly strong among women consuming alcohol. Copyright (C) 2015 Wolters Kluwer Health, Inc. All rights reserved.