title: Mammographic density and breast cancer risk by family history in women of white and Asian ancestry.
abstract: OBJECTIVE
  Mammographic density, i.e., the radiographic appearance of the breast, is a strong predictor of breast cancer risk. To determine whether the association of breast density with breast cancer is modified by a first-degree family history of breast cancer (FHBC) in women of white and Asian ancestry, we analyzed data from four case-control studies conducted in the USA and Japan.
  
  
  METHODS
  The study population included 1,699 breast cancer cases and 2,422 controls, of whom 45% reported white (N = 1,849) and 40% Asian (N = 1,633) ancestry. To standardize mammographic density assessment, a single observer re-read all mammograms using one type of interactive thresholding software. Logistic regression was applied to estimate odds ratios (OR) while adjusting for confounders.
  
  
  RESULTS
  Overall, 496 (12%) of participants reported a FHBC, which was significantly associated with breast cancer risk in the adjusted model (OR 1.51; 95% CI 1.23-1.84). There was a statistically significant interaction on a multiplicative scale between FHBC and continuous percent density (per 10 % density: p = 0.03). The OR per 10% increase in percent density was higher among women with a FHBC (OR 1.30; 95% CI 1.13-1.49) than among those without a FHBC (OR 1.14; 1.09-1.20). This pattern was apparent in whites and Asians. The respective ORs were 1.45 (95% CI 1.17-1.80) versus 1.22 (95% CI 1.14-1.32) in whites, whereas the values in Asians were only 1.24 (95% CI 0.97-1.58) versus 1.09 (95% CI 1.00-1.19).
  
  
  CONCLUSIONS
  These findings support the hypothesis that women with a FHBC appear to have a higher risk of breast cancer associated with percent mammographic density than women without a FHBC.
authors.affiliation: University of Hawaii Cancer Center, 701 Ilalo Street, Honolulu, HI, 96813, USA, gertraud@cc.hawaii.edu.
authors.forename: Gertraud
authors.initials: G
authors.lastname: Maskarinec
authors.forename: Kaylae L
authors.initials: KL
authors.lastname: Nakamura
authors.forename: Christy G
authors.initials: CG
authors.lastname: Woolcott
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Conroy
authors.forename: Celia
authors.initials: C
authors.lastname: Byrne
authors.forename: Chisato
authors.initials: C
authors.lastname: Nagata
authors.forename: Giske
authors.initials: G
authors.lastname: Ursin
authors.forename: Celine M
authors.initials: CM
authors.lastname: Vachon
mesh_terms: D000328:Adult; D000368:Aged; D044466:Asian People; D001940:Breast / Q000473:pathology*; D000071060:Breast Density; D001943:Breast Neoplasms / Q000453:epidemiology*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D042361:Mammary Glands, Human / Q000002:abnormalities*; D008327:Mammography; D008875:Middle Aged; D016017:Odds Ratio; D012307:Risk Factors; D044465:White People