Changes in the Breast Cancer Risk Distribution among Women Utilizing Screening Mammography in Vermont Between 2001 and 2012

Abstract

We previously reported a decline in overall breast cancer screening rates in Vermont following 2009. During this period, there has been debate regarding the role of patient context in decisions about when and how often to get screened, as well as increased interest in risk- based screening to optimize the balance between the potential benefits and harms of screening. The purpose of the current study was to evaluate whether the breast cancer risk distribution of the screened population in Vermont has changed during the observed decline in utilization rates. We examined the distribution of breast cancer risk among the screened population in Vermont from 2001 to 2012 using cross-sectional data from the statewide Vermont Breast Cancer Surveillance System. We employed the Breast Cancer Surveillance Consortium risk model to estimate each individual's risk of developing breast cancer within 5 years according to age, breast density, race/ethnicity, family history of breast cancer, and biopsy history. Among women ages 40 to 74 who received screening mammograms, the absolute number of visits dropped by 4,257, from 54,415 to 50,158 (−7.3%; 95% CI: −7.5, −7.1) between 2009 and 2012. Concurrently, the number of screened women who were estimated to be at low risk of developing breast cancer decreased by 4,240 (95% CI: 3,907, 4,573), representing the bulk of the overall decrease. There was no significant change in the aggregate number of women estimated to be at higher risk (−17 women; 95% CI: −350, 316). The outsized proportion of the decline attributed to women at low estimated risk held across younger and older age groups: among women ages 40 to 49, the absolute number screened dropped by 3,337, with 2,495 (95% CI: 2,389, 2,601) reflected by declines among women at low risk; among women ages 50 to 74, the absolute number screened dropped by only 920, however this value reflects a decrease of 1,763 (95% CI: 1,519, 2,007) for the low risk category, and gains totaling 843 (95% CI: 599, 1,087) among higher risk categories. We conclude that the observed decline in women screened in Vermont since 2009 is largely attributable to reductions in visits by women who are estimated to be at low risk of developing breast cancer, and that this trend generally holds across age groups.