Objectives: The aim of this study was to assess the effects of service screening mammography on breast carcinoma incidence and refined mortality among women aged 55–69 at entry in three cities employing different screening policies.
Methods: Since 1987, the city of Turku, Finland, has provided service screening mammography for women aged 55–69 at entry (in 1987), and Tampere provided screening for women aged 55–59 at entry, whereas Helsinki did not screen any of these age groups. The incidence of breast carcinoma during the screening period 1987–97 in women born in 1918–32 (1918–22, 1923–27, 1928–32) was compared with incidence during the pre-screening period 1976–86 in women born in 1907–21 (1907–11, 1912–16, 1917–21) in each city. The follow-up for mortality was four years longer.
Results: Breast carcinoma incidence was 31–38% higher in the screening period in all three cities irrespective of screening. In breast carcinoma mortality, no significant changes were seen in Helsinki or Tampere. In Turku, a 36% mortality reduction (relative risk [RR] 0.64; 95% confidence interval [CI] 0.47–0.88; P=0.007) in the whole study population and a 47% reduction in women aged 65–69 at entry (RR 0.53; 95% CI 0.28–0.99; P=0.047) were seen.
Conclusions: The incidence of breast carcinoma increased in all study cities irrespective of screening. The comprehensive screening programme in Turku including women aged 55–69 at entry was associated with a significant reduction in breast carcinoma mortality. The pronounced decrease in mortality in the oldest age group (65–69 years at entry) also indicated that women of this age group greatly benefit from mammography screening.
