Abstract
BACKGROUND: Breast cancer incidence and mortality are influenced by early-detection methods, including mammographic screening. Demographic changes in US statistics serve as a model for changes that can be anticipated in countries where mammographic screening has not been implemented. METHODS: SEER statistics (1973-2013) for breast cancer mortality, incidence, stage at diagnosis, and age at diagnosis were examined. Temporal associations between screening changes and breast cancer demographics in the US were documented. FINDINGS: Before 1982 (pre-screening), breast cancer incidence in the US remained stable, with similar incidence of localized and regional cancers, and with in-situ disease comprising <2% of diagnosed disease.(1) During the transitional phase of mammographic screening, breast cancer incidence increased. In 1991, breast cancer age-adjusted mortality rates began decreasing and have continued to decrease. In the post-screening phase, stage distribution stabilized, but now with localized and in-situ disease representing the majority of diagnosed cases. The median age at diagnosis has increased to 61 years. DISCUSSION: Mammographic screening increases breast cancer incidence, shifts the stage distribution toward earlier stage disease, and in high-income countries, is associated with improved survival. Whether similar improvement in breast cancer survival can be achieved in the absence of mammographic screening has yet to be conclusively demonstrated.