Nationwide mammographic screening and breast cancer mortality in Taiwan: an interrupted time-series analysis.

Background: In Taiwan, breast cancer is the third leading cause of cancer death in women. A nationwide screening program with biennial mammography for women aged 40-69 in Taiwan was implemented since July 2004, but the impact on breast cancer mortality has not been investigated.

Methods: The interrupted time-series analysis was used to estimate the impact of mammographic screening on temporal trends of breast cancer mortality and to calculate the level of temporal changes due to the mammographic screening.

Results: The annual average percentage changes of the age-standardized breast cancer mortality rates for all women aged 40-69 were 1.06% from 1991 to 2004 (before mammographic screening) and 0.33-0.34% from 2005 to 2019 (after mammographic screening). For all women aged 40-69, the results of interrupted time-series analysis showed that the increasing trends of breast cancer mortality were all attenuated after the implementation of mammographic screening. An estimation of 2114 women prevented from death of breast cancer may be attributable to screening. For women aged 40-44, 55-59, 60-64 and 65-69, the percentage changes in mortality rates were - 12.1% (- 5.1 to - 19.6%), - 20.8% (- 16.5 to - 25.2%), - 12.8% (- 8.5 to - 17.3%) and - 13.0% (- 7.9 to - 18.3%), respectively, after screening. For women aged 45-49 and 50-54, the reduction of deaths and mortality rates of breast cancer were a little.

Conclusions: This study revealed that the nationwide screening program with biennial mammography may be associated with the attenuation of breast cancer mortality trends in women aged 40-69 in Taiwan.