title: Efficacy of breast cancer screening in the community according to risk level.
abstract: BACKGROUND
  The efficacy of breast cancer screening in the community may differ from that suggested by the results of randomized trials, and no data have been available on efficacy among women who have different levels of breast cancer risk.
  
  
  METHODS
  We conducted a matched case-control study among women enrolled in six health plans in Washington, Oregon, California, Massachusetts, and Minnesota. We examined the efficacy of screening by mammography and/or clinical breast examination among women in two age cohorts (40-49 years and 50-65 years) and in two breast cancer risk levels (average and increased risk). Women who died from breast cancer from January 1, 1983, through December 31, 1998, (N = 1351; case subjects) were matched to control subjects (N = 2501) on age and risk level. Increased risk was defined as a family history of breast cancer or a breast biopsy noted in the medical records before the index date (defined as date of first suspicion of breast abnormalities in case subjects, with the same date used for matched control subjects). Data on screening, risk status, and other variables were abstracted from medical records. Conditional logistic regression was used to examine the association between breast cancer mortality and receipt of screening. All statistical tests were two-sided.
  
  
  RESULTS
  There were small, non-statistically significant associations between breast cancer mortality and receipt of screening during the 3 years prior to the index date for both the younger women [odds ratio (OR) = 0.92; 95% confidence interval (CI) = 0.76 to 1.13] and the older women (OR = 0.87; 95% CI = 0.68 to 1.12). The association among women at increased risk (OR = 0.74; 95% CI = 0.50 to 1.03) was stronger than that among women at average risk (OR = 0.96; 95% CI = 0.80 to 1.14), but the difference was not statistically significant (P = .17).
  
  
  CONCLUSIONS
  In this community-based study, screening history was not associated with breast cancer mortality. However, potential limitations of this study argue for a cautious interpretation of these findings.
authors: School of Medicine, Harborview Medical Center, University of Washington, Seattle, WA, USA. jelmore@u.washington.edu
authors: Joann G
authors: JG
authors: Elmore
authors: Lisa M
authors: LM
authors: Reisch
authors: Mary B
authors: MB
authors: Barton
authors: William E
authors: WE
authors: Barlow
authors: Sharon
authors: S
authors: Rolnick
authors: Emily L
authors: EL
authors: Harris
authors: Lisa J
authors: LJ
authors: Herrinton
authors: Ann M
authors: AM
authors: Geiger
authors: R Kevin
authors: RK
authors: Beverly
authors: Gene
authors: G
authors: Hart
authors: Onchee
authors: O
authors: Yu
authors: Sarah M
authors: SM
authors: Greene
authors: Noel S
authors: NS
authors: Weiss
authors: Suzanne W
authors: SW
authors: Fletcher
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000175:diagnosis* / Q000000981:diagnostic imaging / Q000401:mortality / Q000517:prevention & control*; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008327:Mammography; D008403:Mass Screening; D008875:Middle Aged; D016017:Odds Ratio; D012107:Research Design; D018570:Risk Assessment; D014481:United States / Q000453:epidemiology