title: Urinary 2-hydroxyestrone/16alpha-hydroxyestrone ratio and risk of breast cancer in postmenopausal women.
abstract: BACKGROUND
  It has been suggested that women who metabolize a larger proportion of their endogenous estrogen via the 16alpha-hydroxylation pathway may be at elevated risk of breast cancer compared with women who metabolize proportionally more estrogen via the 2-hydroxylation pathway. However, the supporting epidemiologic data are scant. Consequently, we compared the ratio of urinary 2-hydroxyestrone (2-OHE1) to 16alphahydroxyestrone (16alpha-OHE1) in postmenopausal women with breast cancer and in healthy control subjects.
  
  
  METHODS
  Estrogen metabolites were measured in urine samples obtained from white women who had participated in a previous population-based, breast cancer case-control study at our institution. All P values are from two-sided tests.
  
  
  RESULTS
  All of the urinary estrogens measured, with the exception of estriol, were higher in the 66 case patients than in the 76 control subjects. The mean value of urinary 2-OHE1 in case patients was 13.8% (P = .20) higher than that in control subjects, 16alpha-OHE1 was 12.1% (P = .23) higher, estrone was 20.9% higher (P = .14), and 17beta-estradiol was 12.0% higher (P = .36). The ratio of 2-OHE1 to 16alpha-OHE1 was 1.1% higher in the patients (P = .84), contrary to the hypothesis. Compared with women in the lowest third of the values for the ratio of urinary 2-OHE1 to 16alpha-OHE1, women in the highest third were at a nonstatistically significantly increased risk of breast cancer (odds ratio = 1.13; 95% confidence interval = 0.46-2.78), again contrary to the hypothesis.
  
  
  CONCLUSIONS
  This study does not support the hypothesis that the ratio of the two hydroxylated metabolites (2-OHE1/16alpha-OHE1) is an important risk factor for breast cancer.
authors.affiliation: Department of Preventive Medicine, University of Southern California/Norris Comprehensive Cancer Center, Los Angeles 90033, USA.
authors.forename: G
authors.initials: G
authors.lastname: Ursin
authors.forename: S
authors.initials: S
authors.lastname: London
authors.forename: F Z
authors.initials: FZ
authors.lastname: Stanczyk
authors.forename: E
authors.initials: E
authors.lastname: Gentzschein
authors.forename: A
authors.initials: A
authors.lastname: Paganini-Hill
authors.forename: R K
authors.initials: RK
authors.lastname: Ross
authors.forename: M C
authors.initials: MC
authors.lastname: Pike
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000652:urine*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D006894:Hydroxyestrones / Q000652:urine*; D007124:Immunoenzyme Techniques; D008875:Middle Aged; D016017:Odds Ratio; D017698:Postmenopause / Q000652:urine*; D011863:Radioimmunoassay; D012306:Risk; D012307:Risk Factors; D039181:Steroid 16-alpha-Hydroxylase
chemical_list: D006894:Hydroxyestrones; C026702:16-hydroxyestrone; D039181:Steroid 16-alpha-Hydroxylase; C024980:2-hydroxyestrone