Abstract
Breast cancer (BC) is the most common cancer in Kazakhstan, and a population-based breast cancer screening program was introduced in 2008, initially targeting women aged 50-60 years. It was subsequently expanded in 2018 to include women aged 40-70 years. This study evaluates the national BC screening program from its introduction in 2008 onward, focusing on program outputs, outcomes, and associated expenditures. Several administrative datasets and official sources were analyzed, including the legislative acts database, analytical reports on cancer screening programs, and cancer reporting forms. Trends in key indicators were summarized using the average annual percent change (AAPC). From the program's inception, the absolute number of women screened increased steadily, with an AAPC of 6.23%. In contrast, the proportion of eligible women covered by screening declined over time, particularly following the expansion of the target age groups in 2018. Stage I BC detected through screening accounted for only about 50% of all stage I BC cases diagnosed nationwide, while the contribution of screening to stage II cancers was below 30%. Neither the introduction nor the subsequent expansion of the BC screening program was associated with statistically significant immediate or trend changes in national BC incidence or mortality rates. These findings may inform evidence-based discussions on potential refinements to BC screening policy and practice in Kazakhstan.