The Swedish two-county trial twenty years later - Updated mortality results and new insights from long-term follow-up

This article updates the results 20 years later of the Swedish Two-County T rial of mammographic screening for breast cancer. The result remains a subs tantial and significant 32% reduction in breast cancer mortality in associa tion with an invitation to be screened. It is shown that the effect of scre ening can be ascribed to a shift in the prognostic character of the tumors diagnosed, that in turn can be used as a measure of the quality of a screen ing program. The results on prognosis also identify a group of small but hi gh-risk tumors, with fundamental implications for diagnosis and treatment.