Screening programmes and breast cancer mortality: an observational study of 194 countries.

Objective: To investigate the associations between national breast cancer screening programmes and breast cancer mortality globally. Methods: We collected data on breast cancer screening programmes and breast cancer mortality from the World Health Organization's Global Health Observatory, the Global Burden of Diseases 2021 study and the Eurostat database. We assessed differences in breast cancer mortality between countries with regular and irregular screening programmes, adjusting for sociodemographic index. We calculated annual changes in breast cancer mortality from 2015 to 2021 and assessed differences in mortality changes between countries with regular and irregular screening programmes. Findings: Between 2015 and 2021, 94 of 194 countries reported having national breast cancer screening programmes. In 2021, countries with regular breast cancer screening programmes had 3.74 fewer deaths (95% uncertainty interval, UI: 1.69-5.81) per 100 000 population than countries with irregular screening programmes. This difference was more pronounced in women aged 50-74 years: 10.13 fewer deaths (95% UI: 4.47-15.80) per 100 000. From 2015 to 2021, the age-standardized mortality rate decreased by 1.02% (95% UI: 0.71-1.36) annually in countries with regular breast cancer screening programmes, whereas countries with irregular programmes had an annual increase of 0.45% (95% UI: 0.23-0.69). Higher breast cancer screening coverage rates were associated with lower mortality in the European region. Conclusion: Countries with breast cancer screening programmes had a significant reduction in breast cancer mortality. Reducing breast cancer mortality globally will require adopting national breast cancer screening programmes and increasing screening coverage, particularly among women aged 50-74 years.