title: Breast cancer risk in relation to urinary and serum biomarkers of phytoestrogen exposure in the European Prospective into Cancer-Norfolk cohort study.
abstract: BACKGROUND
  Phytoestrogens are a group of compounds found in plants that structurally resemble the hormone oestradiol, and thus have the potential to act as oestrogen agonists or antagonists. Their potential effects may alter the risk of breast cancer, but only a limited range of phytoestrogens has been examined in prospective cohort studies.
  
  
  METHODS
  Serum and urine samples from 237 incident breast cancer cases and 952 control individuals (aged 45 to 75 years) in the European Prospective into Cancer-Norfolk cohort were analysed for seven phytoestrogens (daidzein, enterodiol, enterolactone, genistein, glycitein, o-desmethylangolensin, and equol) using liquid chromatography/mass spectrometry. Data on participants' diet, demographics, anthropometrics, and medical history were collected upon recruitment. All models were adjusted for weight, fat and energy intake, family history of breast cancer, social class, analytical batch, and factors related to oestrogen exposure.
  
  
  RESULTS
  Urinary or serum phytoestrogens were not associated with protection from breast cancer in the European Prospective into Cancer-Norfolk cohort. Breast cancer risk was marginally increased with higher levels of total urinary isoflavones (odds ratio = 1.08 (95% confidence interval = 1.00 to 1.16), P = 0.055); among those with oestrogen receptor-positive tumours, the risk of breast cancer was increased with higher levels of urinary equol (odds ratio = 1.07 (95% confidence interval = 1.01 to 1.12), P = 0.013).
  
  
  CONCLUSIONS
  There was limited evidence of an association between phytoestrogen biomarkers and breast cancer risk in the present study. There was no indication of decreased likelihood of breast cancer with higher levels of phytoestrogen biomarkers, but the observation that some phytoestrogen biomarkers may be associated with greater risk of breast cancer warrants further study with greater statistical power.
authors.affiliation: MRC Centre for Nutrition and Cancer, Department of Public Health and Primary Care, Institute of Public Health, University of Cambridge, Strangeways Research Laboratory, Wort's Causeway, Cambridge, CB1 8RN, UK. heather.ward@srl.cam.ac.uk
authors.forename: Heather
authors.initials: H
authors.lastname: Ward
authors.forename: Gaelle
authors.initials: G
authors.lastname: Chapelais
authors.forename: Gunter G C
authors.initials: GG
authors.lastname: Kuhnle
authors.forename: Robert
authors.initials: R
authors.lastname: Luben
authors.forename: Kay-Tee
authors.initials: KT
authors.lastname: Khaw
authors.forename: Sheila
authors.initials: S
authors.lastname: Bingham
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood* / Q000652:urine*; D001943:Breast Neoplasms / Q000097:blood* / Q000652:urine*; D015331:Cohort Studies; D005260:Female; D006304:Health Status; D006801:Humans; D008019:Life Style; D008875:Middle Aged; D048789:Phytoestrogens / Q000097:blood* / Q000652:urine*; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D011795:Surveys and Questionnaires
chemical_list: D014408:Biomarkers, Tumor; D048789:Phytoestrogens