title: Circulating carotenoids and risk of breast cancer: pooled analysis of eight prospective studies.
abstract: BACKGROUND
  Carotenoids, micronutrients in fruits and vegetables, may reduce breast cancer risk. Most, but not all, past studies of circulating carotenoids and breast cancer have found an inverse association with at least one carotenoid, although the specific carotenoid has varied across studies.
  
  
  METHODS
  We conducted a pooled analysis of eight cohort studies comprising more than 80% of the world's published prospective data on plasma or serum carotenoids and breast cancer, including 3055 case subjects and 3956 matched control subjects. To account for laboratory differences and examine population differences across studies, we recalibrated participant carotenoid levels to a common standard by reassaying 20 plasma or serum samples from each cohort together at the same laboratory. Using conditional logistic regression, adjusting for several breast cancer risk factors, we calculated relative risks (RRs) and 95% confidence intervals (CIs) using quintiles defined among the control subjects from all studies. All P values are two-sided.
  
  
  RESULTS
  Statistically significant inverse associations with breast cancer were observed for α-carotene (top vs bottom quintile RR = 0.87, 95% CI = 0.71 to 1.05, P(trend) = .04), β-carotene (RR = 0.83, 95% CI = 0.70 to 0.98, P(trend) = .02), lutein+zeaxanthin (RR = 0.84, 95% CI = 0.70 to 1.01, P(trend) = .05), lycopene (RR = 0.78, 95% CI = 0.62 to 0.99, P(trend) = .02), and total carotenoids (RR = 0.81, 95% CI = 0.68 to 0.96, P(trend) = .01). β-Cryptoxanthin was not statistically significantly associated with risk. Tests for heterogeneity across studies were not statistically significant. For several carotenoids, associations appeared stronger for estrogen receptor negative (ER(-)) than for ER(+) tumors (eg, β-carotene: ER(-): top vs bottom quintile RR = 0.52, 95% CI = 0.36 to 0.77, P(trend) = .001; ER(+): RR = 0.83, 95% CI = 0.66 to 1.04, P(trend) = .06; P(heterogeneity) = .01).
  
  
  CONCLUSIONS
  This comprehensive prospective analysis suggests women with higher circulating levels of α-carotene, β-carotene, lutein+zeaxanthin, lycopene, and total carotenoids may be at reduced risk of breast cancer.
authors.affiliation: Channing Division of Network Medicine, Department of Medicine, Brigham & Women's Hospital and Harvard Medical School, 181 Longwood Ave, Boston, MA 02115, USA. heather.eliassen@channing.harvard.edu
authors.forename: A Heather
authors.initials: AH
authors.lastname: Eliassen
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Hendrickson
authors.forename: Louise A
authors.initials: LA
authors.lastname: Brinton
authors.forename: Julie E
authors.initials: JE
authors.lastname: Buring
authors.forename: Hannia
authors.initials: H
authors.lastname: Campos
authors.forename: Qi
authors.initials: Q
authors.lastname: Dai
authors.forename: Joanne F
authors.initials: JF
authors.lastname: Dorgan
authors.forename: Adrian A
authors.initials: AA
authors.lastname: Franke
authors.forename: Yu-tang
authors.initials: YT
authors.lastname: Gao
authors.forename: Marc T
authors.initials: MT
authors.lastname: Goodman
authors.forename: Göran
authors.initials: G
authors.lastname: Hallmans
authors.forename: Kathy J
authors.initials: KJ
authors.lastname: Helzlsouer
authors.forename: Judy
authors.initials: J
authors.lastname: Hoffman-Bolton
authors.forename: Kerstin
authors.initials: K
authors.lastname: Hultén
authors.forename: Howard D
authors.initials: HD
authors.lastname: Sesso
authors.forename: Anne L
authors.initials: AL
authors.lastname: Sowell
authors.forename: Rulla M
authors.initials: RM
authors.lastname: Tamimi
authors.forename: Paolo
authors.initials: P
authors.lastname: Toniolo
authors.forename: Lynne R
authors.initials: LR
authors.lastname: Wilkens
authors.forename: Anna
authors.initials: A
authors.lastname: Winkvist
authors.forename: Anne
authors.initials: A
authors.lastname: Zeleniuch-Jacquotte
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
authors.forename: Susan E
authors.initials: SE
authors.lastname: Hankinson
mesh_terms: D000328:Adult; D000368:Aged; D016588:Anticarcinogenic Agents / Q000097:blood*; D001943:Breast Neoplasms / Q000097:blood / Q000453:epidemiology* / Q000517:prevention & control*; D002338:Carotenoids / Q000097:blood*; D016022:Case-Control Studies; D002851:Chromatography, High Pressure Liquid / Q000379:methods; D003299:Cooperative Behavior; D005260:Female; D005638:Fruit; D006801:Humans; D016015:Logistic Models; D014975:Lutein / Q000097:blood; D000077276:Lycopene; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D014675:Vegetables; D024341:Xanthophylls / Q000097:blood; D065146:Zeaxanthins; D019207:beta Carotene / Q000097:blood
chemical_list: D016588:Anticarcinogenic Agents; D024341:Xanthophylls; D065146:Zeaxanthins; D019207:beta Carotene; D002338:Carotenoids; C041635:alpha-carotene; D000077276:Lycopene; D014975:Lutein