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Updated: Sep 21, 2026
Changes in Mammary Gland Morphology and Breast Cancer Risk in Rats
Published on: October 16, 2010
Demographic changes in breast cancer incidence, stage at diagnosis and age associated with population-based
Francys C Verdial1, Ruth Etzioni2, Catherine Duggan2
1Department of Surgery, University of Washington School of Medicine, Seattle, Washington.
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.
