Service screening mammography reduces breast cancer mortality among elderly women in Turku.

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.