title: Biennial versus annual mammography and the risk of late-stage breast cancer.
abstract: BACKGROUND
  Mammography screening may reduce breast cancer mortality by detecting cancers at an earlier stage. However, certain questions remain, including the ideal interval between mammograms.
  
  
  METHODS
  We conducted an observational study using information collected by seven mammography registries across the United States to investigate whether women diagnosed with breast cancer after having screening mammograms separated by a 2-year interval (n = 2440) are more likely to be diagnosed with late-stage disease (positive lymph nodes or metastases) than women diagnosed with breast cancer after having screening mammograms separated by a 1-year interval (n = 5400). Analyses were stratified by age and breast density to clarify whether groups that have the poorest mammography sensitivity (i.e., women under age 50 years and those with mammographically dense breasts) would benefit most from annual screening. The subjects were women diagnosed with breast cancer between 1996 and 2001 who were 40-89 years old at their index mammographic examination (i.e., the most recent screen at or before breast cancer diagnosis). Data were analyzed by logistic regression, adjusting for race, ethnicity, family history of breast cancer, and mammography registry.
  
  
  RESULTS
  Among women age 40-49 years at the index mammogram, those with a 2-year screening interval were more likely to have late-stage disease at diagnosis than those with a 1-year screening interval (28% versus 21%; odds ratio [OR] = 1.35, 95% confidence interval [CI] = 1.01 to 1.81). There was no increase in late-stage disease for women 50 years or older with a 2-year versus a 1-year screening interval (women age 50-59 years at index mammogram: OR = 0.97, 95% CI = 0.75 to 1.25; women age 60-69 years at index mammogram: OR = 0.99, 95% CI = 0.72 to 1.35; women age 70 years or older at index mammogram: OR = 0.88, 95% CI = 0.64 to 1.19). There was no indication that women with dense breasts would benefit more from a 1-year versus 2-year screening interval than women with fatty breasts.
  
  
  CONCLUSIONS
  These findings may be useful for policy decisions about appropriate screening intervals and for use in statistical models that estimate the costs and benefits of mammography by age and screening interval.
authors.affiliation: School of Public Health, University of Washington, Seattle, WA, USA. ewhite@fhcrc.org
authors.forename: Emily
authors.initials: E
authors.lastname: White
authors.forename: Diana L
authors.initials: DL
authors.lastname: Miglioretti
authors.forename: Bonnie C
authors.initials: BC
authors.lastname: Yankaskas
authors.forename: Berta M
authors.initials: BM
authors.lastname: Geller
authors.forename: Robert D
authors.initials: RD
authors.lastname: Rosenberg
authors.forename: Karla
authors.initials: K
authors.lastname: Kerlikowske
authors.forename: Laura
authors.initials: L
authors.lastname: Saba
authors.forename: Pamela M
authors.initials: PM
authors.lastname: Vacek
authors.forename: Patricia A
authors.initials: PA
authors.lastname: Carney
authors.forename: Diana S M
authors.initials: DS
authors.lastname: Buist
authors.forename: Nina
authors.initials: N
authors.lastname: Oestreicher
authors.forename: William
authors.initials: W
authors.lastname: Barlow
authors.forename: Rachel
authors.initials: R
authors.lastname: Ballard-Barbash
authors.forename: Stephen H
authors.initials: SH
authors.lastname: Taplin
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000000981:diagnostic imaging / Q000473:pathology; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000000981:diagnostic imaging / Q000473:pathology; D016001:Confidence Intervals; D005260:Female; D006801:Humans; D016015:Logistic Models; D008327:Mammography / Q000379:methods* / Q000592:standards; D008875:Middle Aged; D009367:Neoplasm Staging; D016017:Odds Ratio; D018579:Patient Selection; D012042:Registries; D012107:Research Design; D013997:Time Factors; D014481:United States