title: Mammographic features associated with interval breast cancers in screening programs.
abstract: BACKGROUND
  Percent mammographic density (PMD) is associated with an increased risk of interval breast cancer in screening programs, as are younger age, pre-menopausal status, lower body mass index and hormone therapy. These factors are also associated with variations in PMD. We have examined whether these variables influence the relative frequency of interval and screen-detected breast cancer, independently or through their associations with PMD. We also examined the association of tumor size with PMD and dense and non-dense areas in screen-detected and interval breast cancers.
  
  
  METHODS
  We used data from three case-control studies nested in screened populations. Interval breast cancer was defined as invasive breast cancer detected within 12 months of a negative mammogram. We used a computer-assisted method of measuring the dense and total areas of breast tissue in the first (baseline) mammogram taken at entry to screening programs and calculated the non-dense area and PMD. We compared these mammographic features, and other risk factors at baseline, in women with screen-detected (n = 718) and interval breast cancer (n = 125).
  
  
  RESULTS
  In multi-variable analysis, the baseline characteristics of younger age, greater dense area and smaller non-dense mammographic area were significantly associated with interval breast cancer compared to screen-detected breast cancer. Compared to screen-detected breast cancers, interval cancers had a larger maximum tumor diameter within each mammographic measure.
  
  
  CONCLUSIONS
  Age and the dense and non-dense areas in the baseline mammogram were independently associated with interval breast cancers in screening programs. These results suggest that decreased detection of cancers caused by the area of dense tissue, and more rapid growth associated with a smaller non-dense area, may both contribute to risk of interval breast cancer. Tailoring screening to individual mammographic characteristics at baseline may reduce the number of interval cancers.
authors.forename: Norman F
authors.initials: NF
authors.lastname: Boyd
authors.forename: Ella
authors.initials: E
authors.lastname: Huszti
authors.forename: Olga
authors.initials: O
authors.lastname: Melnichouk
authors.forename: Lisa J
authors.initials: LJ
authors.lastname: Martin
authors.forename: Greg
authors.initials: G
authors.lastname: Hislop
authors.forename: Anna
authors.initials: A
authors.lastname: Chiarelli
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Yaffe
authors.forename: Salomon
authors.initials: S
authors.lastname: Minkin
mesh_terms: D000328:Adult; D000071060:Breast Density; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000473:pathology; D002170:Canada; D016022:Case-Control Studies; D055088:Early Detection of Cancer; D005260:Female; D006801:Humans; D042361:Mammary Glands, Human / Q000002:abnormalities*; D008327:Mammography; D008875:Middle Aged; D016017:Odds Ratio; D012306:Risk; D012307:Risk Factors; D047368:Tumor Burden