BACKGROUND: Screening with mammography has been shown by randomized controlled trials to reduce @entity0 mortality in @entity1 aged 40 to 74 years. Estimates from observational studies following screening implementation in different countries have produced varyied findings. We report findings for seven Canadian breast screening programs. METHODS: Canadian breast screening programs were invited to participate in a study aimed at comparing @entity0 mortality in @entity1 and nonparticipants. Seven of 12 programs, representing 85% of the Canadian population, participated in the study. Data were obtained from the screening programs and corresponding @entity5 registries on screening mammograms and @entity0 diagnoses and deaths for the period between 1990 and 2009. Standardized mortality ratios were calculated comparing observed mortality in @entity1 to that expected based upon nonparticipant rates. A substudy using data from British Columbia @entity1 aged 35 to 44 years was conducted to assess the potential effect of self-selection participation bias. All statistical tests were two-sided. RESULTS: Data were obtained on 2796472 screening @entity1 . The average @entity0 mortality among @entity1 was 40% (95% confidence interval [CI] = 33% to 48%) lower than expected, with a range across provinces of 27% to 59%. Age at entry into screening did not greatly affect the magnitude of the average reduction in mortality, which varied between 35% and 44% overall. The substudy found no evidence that self-selection biased the reported mortality results, although the confidence intervals of this assessment were wide. CONCLUSION: Participation in mammography screening programs in Canada was associated with substantially reduced @entity0 mortality.

Pan-Canadian study of mammography screening and mortality from XXXX .

@entity1 :: ('9606', 'Species') :: ['participants', 'women'] @entity5 :: ('MESH:D009369', 'Disease') :: ['cancer'] @entity0 :: ('MESH:D001943', 'Disease') :: ['breast cancer']
@entity0 :: (MESH:D001943,Disease) :: ['breast cancer']
