Breast cancer screening as public health policy in Finland.

A nationwide mammographic screening for breast cancer was started in Finland in 1987. During the first 2 years of the organised screening programme, 126,000 women were invited. Most of them (103,000) belonged to the birth year cohort in the 50-59 years' age groups. Among the 112,000 screenees, 418 cancers (0.4%) were found. Specificity of the test was about 96%. The screening prevalence was 2.4 times the annual incidence and a minimum estimate for the detection rate among those invited was 1.6 times that among those not invited. These estimates indicate a relatively low test and programme sensitivity. The final effectiveness of a public health policy cannot be predicted on the basis of limited preventive trials, and there is need to evaluate also a public health policy by experimental means.