title: Investigation of mammographic breast density as a risk factor for ovarian cancer.
abstract: BACKGROUND
  Endogenous hormones and growth factors that increase mammographic breast density could increase ovarian cancer risk. We examined whether high breast density is associated with ovarian cancer risk.
  
  
  METHODS
  We conducted a cohort study of 724,603 women aged 40 to 79 years with 2,506,732 mammograms participating in the Breast Cancer Surveillance Consortium from 1995 to 2009. Incident epithelial ovarian cancer was diagnosed in 1373 women. We used partly conditional Cox regression to estimate the association between breast density and 5-year risk of incident epithelial ovarian cancer overall and stratified by 10-year age group. All statistical tests were two-sided.
  
  
  RESULTS
  Compared with women with scattered fibroglandular densities, women with heterogeneously dense and extremely dense breast tissue had 20% and 18% increased 5-year risk of incident epithelial ovarian cancer (hazard ratio [HR] = 1.20, 95% confidence interval [CI] = 1.06 to 1.36; HR = 1.18, 95% CI = 0.93 to 1.50, respectively; P(trend) = .01). Among women aged 50 to 59 years, we observed a trend in elevated risk associated with increased breast density (P(trend) = .02); women with heterogeneously and extremely dense breast tissue had 30% (HR = 1.30; 95% CI = 1.03 to 1.64) and 65% (HR = 1.65; 95% CI = 1.12 to 2.44) increased risk, respectively, compared with women with scattered fibroglandular densities. The pattern was similar but not statistically significant at age 40 to 49 years. There were no consistent patterns of breast density and ovarian cancer risk at age 60 to 79 years.
  
  
  CONCLUSIONS
  Dense breast tissue was associated with a modest increase in 5-year ovarian cancer risk in women aged 50 to 59 years but was not associated with ovarian cancer at ages 40 to 49 or 60 to 79 years.
authors.affiliation: Affiliations of authors: Group Health Research Institute, Group Health Cooperative, Seattle, WA (KJW, ESO, DLM, DSMB); Department of Medicine and Epidemiology and Biostatistics, General Internal Medicine Section, Department of Veterans Affairs, University of California, San Francisco, San Francisco, CA (KK); Division of Biostatistics, Department of Public Health Sciences, University of California Davis School of Medicine, Davis, CA (DLM, CYM); Department of Obstetrics and Gynecology, University of New Mexico, Albuquerque, NM (CYM); Department of Community and Family Medicine, Norris Cotton Cancer Center, Dartmouth Medical School, Hanover, NH (TO); Department of Surgery and Office of Health Promotion Research, University of Vermont, Burlington, VT (BLS); Department of Radiology, University of North Carolina, Chapel Hill, NC (LMH).
authors.forename: Karen J
authors.initials: KJ
authors.lastname: Wernli
authors.forename: Ellen S
authors.initials: ES
authors.lastname: O'Meara
authors.forename: Karla
authors.initials: K
authors.lastname: Kerlikowske
authors.forename: Diana L
authors.initials: DL
authors.lastname: Miglioretti
authors.forename: Carolyn Y
authors.initials: CY
authors.lastname: Muller
authors.forename: Tracy
authors.initials: T
authors.lastname: Onega
authors.forename: Brian L
authors.initials: BL
authors.lastname: Sprague
authors.forename: Louise M
authors.initials: LM
authors.lastname: Henderson
authors.forename: Diana S M
authors.initials: DS
authors.lastname: Buist
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D001940:Breast / Q000473:pathology*; D000077216:Carcinoma, Ovarian Epithelial; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008327:Mammography; D008875:Middle Aged; D009375:Neoplasms, Glandular and Epithelial / Q000453:epidemiology* / Q000401:mortality; D016017:Odds Ratio; D010051:Ovarian Neoplasms / Q000453:epidemiology* / Q000401:mortality; D018570:Risk Assessment; D012307:Risk Factors; D057566:Self Report; D011795:Surveys and Questionnaires; D014481:United States / Q000453:epidemiology