EFFECTIVENESS OF SCREENING FOR BREAST-CANCER IN WOMEN UNDER 50 YEARS AT ENTRY - THE KOTKA PILOT PROJECT IN FINLAND

It is still uncertain whether mammography is beneficial to women under 50 years of age. We report a follow-up of 41-year birth cohorts in 13 Finnish municipalities subjected to service screening. The women in t hese cohorts were born in even calendar years and they were 40-47 year s old at the time of first screening, which was repeated every other y ear. At the beginning, 4,163 women were invited and 86% attended. Wome n were screened with mammography, physical breast examination and info rmation on detection and early diagnosis of breast cancer by breast se lf-examination (BSE) was given. Incident cases of breast cancer and br east-cancer deaths were recorded. The expected numbers of incident bre ast-cancer cases and deaths from breast cancer were derived from contr ol women who were residents of the same municipalities but who were bo rn in adjacent calendar years (odd years) to those screened. In the sc reened cohorts 13 cancers were screen-detected, 32 cancers were interv al eases and 8 cases were diagnosed among the non-attenders, while in the controls 85 cancers were detected during a 9-year follow-up from 1 982 to 1990. One death from breast cancer occurred in the screened coh orts among cases diagnosed between 1982 and 1990, against 10 expected breast-cancer deaths during a 10-year follow-up from 1982 to 1991 of w omen initially free of breast cancer. Breast-cancer mortality in the s creened cohorts was significantly lower than in the controls (Rate Rat io 0.11), but it is not clear how much of the reduction in mortality c ould be accounted for by the mammography itself and how much to other activities included in the screening programme (especially training in BSE) or to chance variation. It is unlikely that a programme sensitiv ity of 25% (13/53) would have resulted in 89% (100-11) effectiveness o r reduction in the risk of death from breast cancer. (C) 1995 Wiley-Li ss, Inc.