title: Obesity, hormone therapy, estrogen metabolism and risk of postmenopausal breast cancer.
abstract: Hormone therapy (HT) and body mass index (BMI) have been associated with postmenopausal breast cancer. Because estrogen metabolism may affect breast cancer risk and can be altered by weight and HT, it might play a role in the HT-BMI-breast cancer associations. We undertook a nested case-control study within the Observational Study of the Women's Health Initiative. Baseline levels of 2- and 16alpha-hydroxy estrone (2-OHE1 and 16alpha-OHE1) were measured in 200 women who developed breast cancer during follow-up and 200 healthy controls matched to cases by ethnicity, enrollment date, clinic site, type of HT and years since menopause. Wilcoxon nonparametric tests were used to compare estrogen metabolite levels between cases and controls. Conditional logistic regression was used to assess the relationship between BMI, estrogen metabolites and breast cancer risk. 16alpha-OHE1 levels were modestly but significantly higher in HT users among cases (median 356 pg/ml vs. 315 pg/ml) and controls (354 pg/ml vs. 298 pg/ml). 2-OHE1 levels were substantially and significantly higher in HT users among cases (369 pg/ml vs. 125 pg/ml) and controls (347 pg/ml vs. 134 pg/ml). For non-HT users only, greater BMI and higher 16alpha-OHE1 levels were individually and jointly associated with increased breast cancer risk (OR for women with high BMI and high 16alpha-OHE1 compared to those with low BMI and low 16alpha-OHE1 = 3.51, 95% CI = 1.34-9.16). No associations between BMI, estrogen metabolism and breast cancer risk were found for HT users. Estrogen metabolism differs according to both BMI and HT use, potentially explaining the interaction between BMI and HT in relation to breast cancer risk.
authors.affiliation: Department of Epidemiology, Graduate School of Public Health, University of Pittsburgh, 516A Parran Hall, 130 DeSoto Street, Pittsburgh, PA 15261, USA. modugno+@pitt.edu
authors.forename: Francesmary
authors.initials: F
authors.lastname: Modugno
authors.forename: Kevin E
authors.initials: KE
authors.lastname: Kip
authors.forename: Barbara
authors.initials: B
authors.lastname: Cochrane
authors.forename: Lewis
authors.initials: L
authors.lastname: Kuller
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Klug
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Rohan
authors.forename: Rowan T
authors.initials: RT
authors.lastname: Chlebowski
authors.forename: Norman
authors.initials: N
authors.lastname: Lasser
authors.forename: Marcia L
authors.initials: ML
authors.lastname: Stefanick
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000378:metabolism* / Q000473:pathology; D004198:Disease Susceptibility; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D004967:Estrogens / Q000009:adverse effects / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008875:Middle Aged; D009765:Obesity / Q000139:chemically induced / Q000378:metabolism*; D017698:Postmenopause / Q000502:physiology*; D012307:Risk Factors
chemical_list: D004967:Estrogens