Reduction in breast cancer mortality due to the introduction of mass screening in the Netherlands: comparison with the United Kingdom

Objective-To assess the impact of the national breast cancer screening prog ramme on breast cancer mortality in the first years after its introduction. Setting-The Netherlands and United Kingdom. Methods-MISCAN models, incorporating demographic, epidemiological, and scre ening characteristics of the region under study, were used to assess the mo rtality in the presence and absence of screening. Results-Breast cancer mortality decreased in women aged 55-74 as the Dutch nationwide screening programme built up, and was 5% lower in 1996 than befo re the start of the programme. The mortality reduction due to screening in the age group 55-74 is expected to increase gradually to 18% in 1999, 10 ye ars after the introduction of screening, and to 29% in the long term. In th e United Kingdom screening was expected to achieve a mortality reduction of 5% and 18% in the age group 55-69 five and 10 years respectively after scr eening was started. A maximum mortality reduction of 24% in this age group is predicted. Conclusions-The effects of screening will be small in the first years after the start of the programme. Accordingly, it was expected that the reductio n in breast cancer mortality due to the Dutch nationwide breast screening p rogramme, which started around 1989, would be statistically significant fro m 1997 onwards, the point at which the target population of women was compl etely covered; 70% of the reported 12% mortality reduction in England and W ales in 1994 is expected to be attributed to screening.