Mammography screening in three Finnish residential areas: comprehensive population-based study of breast cancer incidence and incidence-based mortality 1976-2009.

Background: The aim of this study was to evaluate the effectiveness of a large-scale screening programme for breast cancer (BC) in Turku, Finland. Incidence and incidence-based mortality (IBM) figures were compared with the areas applying different screening policies.

Methods: Deaths and person-time of women aged 40-84 were assessed for the period 1976-1986 (prescreening era) and the periods 1987-1997 and 1998-2009 (screening periods) using incidence and IBM by age at diagnosis and at death. There was a total of 40.7 million women-years, 83 497 invasive BCs obtained from the Finnish Cancer Registry; 17 508 BC deaths were linked with the data from Statistics Finland.

Results: In Turku, a significant (> 20%) reduction in IBM occurred during 1987-2009 among women aged 60-74 years at diagnosis compared with Helsinki (IBMRR: 0.75, 95% CI: 0.57-1.00), and in women aged 75-84 years at death compared with the rest of Finland (IBMRR: 0.72, 95% CI: 0.53-0.96).

Conclusions: The wide mammography screening programme in Turku was effective in decreasing BC mortality in the elderly age groups. These results support the implementation of BC screening from age 50 up to 74 years.