title: Population-based estimates of the relation between breast cancer risk, tumor subtype, and family history.
abstract: OBJECTIVE
  Many studies that have estimated the breast cancer risk attributable to family history have been based on data collected within family units. Use of this study design has likely overestimated risks for the general population. We provide population-based estimates of breast cancer risk and different tumor subtypes in relation to the degree, number, and age at diagnosis of affected relatives.
  
  
  METHODS
  Cox Proportional Hazards to calculate risks (hazard ratios; 95% confidence interval) of breast cancer and tumor subtypes for women with a family history of breast cancer relative to women without a family history among a cohort of 75,189 women age >or=40 years of whom 1,087 were diagnosed with breast cancer from June 1, 2001-December 31, 2005 (median follow-up 3.16 years).
  
  
  RESULTS
  Breast cancer risk was highest for women with a first-degree family history (1.54; 1.34-1.77); and did not differ substantially by the affected relative's age at diagnosis or by number of affected first-degree relatives. A second-degree family history only was not associated with a significantly increased breast cancer risk (1.15; 0.98-1.35). There was a suggestion that a positive family history was associated with risk of triple positive (Estrogen+/Progesterone+/HER2+) and HER2-overexpressing tumors.
  
  
  CONCLUSIONS
  While a family history of breast cancer in first-degree relatives is an important risk factor for breast cancer, gathering information such as the age at diagnosis of affected relatives or information on second-degree relative history may be unnecessary in assessing personal breast cancer risk among women age >or=40 years.
authors.affiliation: Department of Epidemiology, University of Washington, Seattle, WA, USA. mwelsh@fhcrc.org
authors.forename: Megan L
authors.initials: ML
authors.lastname: Welsh
authors.forename: Diana S M
authors.initials: DS
authors.lastname: Buist
authors.forename: Erin J
authors.initials: EJ
authors.lastname: Aiello Bowles
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Anderson
authors.forename: Joann G
authors.initials: JG
authors.lastname: Elmore
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Li
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology*; D015331:Cohort Studies; D005192:Family Health; D005500:Follow-Up Studies; D020022:Genetic Predisposition to Disease; D006801:Humans; D008875:Middle Aged; D016016:Proportional Hazards Models; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics; D012306:Risk
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases