title: Coffee consumption modifies risk of estrogen-receptor negative breast cancer.
abstract: BACKGROUND
  Breast cancer is a complex disease and may be sub-divided into hormone-responsive (estrogen receptor (ER) positive) and non-hormone-responsive subtypes (ER-negative). Some evidence suggests that heterogeneity exists in the associations between coffee consumption and breast cancer risk, according to different estrogen receptor subtypes. We assessed the association between coffee consumption and postmenopausal breast cancer risk in a large population-based study (2,818 cases and 3,111 controls), overall, and stratified by ER tumour subtypes.
  
  
  METHODS
  Odds ratios (OR) and corresponding 95% confidence intervals (CI) were estimated using the multivariate logistic regression models fitted to examine breast cancer risk in a stratified case-control analysis. Heterogeneity among ER subtypes was evaluated in a case-only analysis, by fitting binary logistic regression models, treating ER status as a dependent variable, with coffee consumption included as a covariate.
  
  
  RESULTS
  In the Swedish study, coffee consumption was associated with a modest decrease in overall breast cancer risk in the age-adjusted model (OR> 5 cups/day compared to OR≤ 1 cup/day: 0.80, 95% CI: 0.64, 0.99, P trend = 0.028). In the stratified case-control analyses, a significant reduction in the risk of ER-negative breast cancer was observed in heavy coffee drinkers (OR> 5 cups/day compared to OR≤ 1 cup/day : 0.43, 95% CI: 0.25, 0.72, P trend = 0.0003) in a multivariate-adjusted model. The breast cancer risk reduction associated with higher coffee consumption was significantly higher for ER-negative compared to ER-positive tumours (P heterogeneity (age-adjusted) = 0.004).
  
  
  CONCLUSIONS
  A high daily intake of coffee was found to be associated with a statistically significant decrease in ER-negative breast cancer among postmenopausal women.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. Jingmei.Li@ki.se
authors.forename: Jingmei
authors.initials: J
authors.lastname: Li
authors.forename: Petra
authors.initials: P
authors.lastname: Seibold
authors.forename: Jenny
authors.initials: J
authors.lastname: Chang-Claude
authors.forename: Dieter
authors.initials: D
authors.lastname: Flesch-Janys
authors.forename: Jianjun
authors.initials: J
authors.lastname: Liu
authors.forename: Kamila
authors.initials: K
authors.lastname: Czene
authors.forename: Keith
authors.initials: K
authors.lastname: Humphreys
authors.forename: Per
authors.initials: P
authors.lastname: Hall
mesh_terms: D000368:Aged; D001943:Breast Neoplasms / Q000737:chemistry / Q000453:epidemiology*; D016022:Case-Control Studies; D003069:Coffee; D004435:Eating; D005260:Female; D006801:Humans; D008875:Middle Aged; D016017:Odds Ratio; D017698:Postmenopause; D011960:Receptors, Estrogen / Q000032:analysis; D012306:Risk
chemical_list: D003069:Coffee; D011960:Receptors, Estrogen