1. Simulation models indicated that annual screening, compared to biennial screening, for high-risk women with dense breasts resulted in a greater number of breast cancer deaths averted.
2. Triennial breast cancer screening for average-risk women with low breast density reduced screening harms without impacting number of breast cancer deaths averted.
Evidence Rating Level: 2 (Good)
Study Rundown: Accepted clinical guidelines currently recommend biennial breast cancer screening for average-risk women aged 50 to 74 years old. However, little data exists regarding alternative screening interventions. The authors of this study sought to evaluate outcomes of three screening intervals—annual, biennial, and triennial—for digital mammography among subgroups of women based on age, risk, and breast density. Collectively, the study suggests that for women with average-risk and lower breast density, extending their screening interval from biennially to triennially is cost effective and may reduce harms of breast cancer screening, such as false-positives and biopsies, without affecting the number of breast cancer deaths averted. In contrast, the benefits of screening frequently increased for women with high breast density and a relative risk (RR) of 2 or greater. Strengths of this study include its large birth cohort and consistent conclusions. However, the simulation models did not address women younger than 50 years of age, those that are carriers of breast cancer susceptibility genes 1 and 2, or those with an RR less than 1, which limit applicability of the results. Overall, the study suggests that risk and breast density level may be useful in guiding screening recommendations in the future.
In-Depth [prospective cohort]: In this analysis, three well-established simulation models were utilized to evaluate several outcomes of breast cancer screening, including life expectancy and QALYs, false-positive mammograms, overdiagnosis, and ratio of false-positive results to breast cancer deaths averted. Specifically, the study showed that among women with average-risk (RR of 1.0 to 1.3) and low breast density, triennial screening resulted in a similar number of breast cancer deaths averted compared to biennial screening for all age groups (50 to 74 years, median of 3.4 to 5.1 vs. 4.1 to 6.5 deaths averted; 65 to 74 years, median of 1.5 to 2.1 vs. 1.8 to 2.6 deaths averted). Comparatively, annual versus biennial screening increased the number of breast cancer deaths averted for women aged 50 to 74 years with any level of breast density and an RR of 4.0, or women aged 65 to 74 years with an RR of 4.0 combined with high breast density.
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