title: Oral contraceptive and reproductive risk factors for ovarian cancer within sisters in the breast cancer family registry.
abstract: BACKGROUND
  Oral contraceptive use has been consistently associated with a reduced risk of ovarian cancer in unrelated, average risk women; however little data exist on whether this benefit extends to higher risk women from cancer families. To examine this, we conducted family-based analyses using the Breast Cancer Family Registry.
  
  
  METHODS
  We used generalised estimating equations to obtain the population average effect across all families (n=389 cases, n=5643 controls) and conditional logistic regression to examine within-family differences in a subset with at least two sisters discordant on ovarian cancer status (n=109 cases, n=149 unaffected sister controls).
  
  
  RESULTS
  In the multivariable generalised estimating equation model there was a reduced risk of ovarian cancer for ever use of oral contraceptives compared with never use (OR=0.58, 95% CI: 0.37, 0.91), and in the conditional logistic model there was a similar inverse association; however, it was not statistically significant (OR=0.52, 95% CI: 0.23, 1.17). We examined this association by BRCA1/2 status and observed a statistically significant reduced risk in the non-carriers only.
  
  
  CONCLUSIONS
  We observed a decreased risk of ovarian cancer with oral contraceptive use supporting that this association observed in unrelated women extends to related women at higher risk.
authors.affiliation: Department of Epidemiology, Columbia University, Mailman School of Public Health, New York, NY 10032, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Ferris
authors.affiliation: Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111-2497, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Daly
authors.affiliation: Huntsman Cancer Institute, University of Utah Health Sciences Center, Salt Lake City, UT 84112, USA.
authors.forename: S S
authors.initials: SS
authors.lastname: Buys
authors.affiliation: Department of Epidemiology, Columbia University, Mailman School of Public Health, New York, NY 10032, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Genkinger
authors.affiliation: Department of Epidemiology, Columbia University, Mailman School of Public Health, New York, NY 10032, USA.
authors.forename: Y
authors.initials: Y
authors.lastname: Liao
authors.affiliation: 1] Department of Epidemiology, Columbia University, Mailman School of Public Health, New York, NY 10032, USA [2] Herbert Irving Comprehensive Cancer Center, Columbia University, New York, NY 10032, USA.
authors.forename: M B
authors.initials: MB
authors.lastname: Terry
mesh_terms: D019313:BRCA1 Protein / Q000235:genetics; D024682:BRCA2 Protein / Q000235:genetics; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics; D003276:Contraceptives, Oral / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008875:Middle Aged; D010051:Ovarian Neoplasms / Q000453:epidemiology* / Q000235:genetics; D012306:Risk; D018570:Risk Assessment; D012307:Risk Factors; D035781:Siblings; D011795:Surveys and Questionnaires
chemical_list: D019313:BRCA1 Protein; C492913:BRCA1 protein, human; D024682:BRCA2 Protein; C551750:BRCA2 protein, human; D003276:Contraceptives, Oral