Abstract

Background: Different levels of breast cancer mortality reduction have been shown in recent case-control studies on the efficacy of population-based breast cancer screening. We looked into how the case-control research design's elements, such as the definition of cases and exposure to screening, affected these discrepancies.

Materials and procedures: We looked at six case-control studies that were carried out in South Australia, The Netherlands, Wales, Iceland, central and northern Italy, and East Anglia (UK).

Results: The difference between screened and unscreened women's breast cancer mortality decreased from 38% to 70% in several case-control studies. We observed design changes, such as whether to include or exclude the first years of screening and the self-selection bias correction factor.

Conclusions: The case-control studies' designs were generally comparable. It is highly improbable that changes in the case-control study design are to blame for the variances in the amount of breast cancer mortality reductions. These variations must be the result of additional elements, such as how the service screening programme is set up and the attendance rate. These case-control studies' estimated decrease in breast cancer mortality suggests that the impact of contemporary mammographic screening is at least consistent with the benefit noted by the previous
randomised screening trials.