1. In this large observational cohort study, screening ultrasonography with mammography was not associated with an improvement in cancer detection rates over mammography alone.
2. Positive predictive value of biopsy recommendation was significantly lower with screening ultrasonography plus mammography compared with mammography alone.
Evidence Rating Level: 2 (Good)
Study Rundown: Breast cancer is responsible for an enormous cost in terms of mortality, morbidity, and health care resources across the world. There is increasing concern that women with denser breasts may have poorer cancer detection rates with screening mammography alone. This was a large observational cohort study of 3,386 women with screening mammography plus ultrasonography (dual screening) compared with 15,176 propensity score-matched women with screening mammography alone. The study found that dual screening was not associated with improvement in cancer detection rates, but was associated with a significant increase in false-positive screens leading to unnecessary biopsies. There was non-significant decrease in false-negative screens with dual screening.
Overall, this study supports existing data that questions the value of screening ultrasonography in addition to mammography when examining women at a wide range of breast cancer risk. The population in this study was lower-risk and heterogeneous and so further studies would be helpful for specific subgroups (i.e., higher risk women).
In-Depth [prospective cohort]: This was an observational cohort study conducted in Vermont and San Francisco comparing screening mammography with ultrasonography (dual screening tests) compared with mammography alone. Data was collected for imaging performed between January 2000 and December 2013. Exclusion criteria included past breast cancer, mastectomy, unilateral examinations, or presence of self-reported symptoms (apart from pain). Total sample size was 18,562 women, with 3386 women with screening ultrasonography plus mammography propensity score matched 1:5 to women with screening mammography alone. Even after matching there were fewer patients in the mammography alone group with high/very high BCSC 5-year breast cancer risk (14.0% vs 21.4%) and results were further adjusted to correct for this. Women were followed for 12 months after screening or until next screening examination, whichever occurred first. Outcomes of interest included cancer detection rates, rates of interval cancer, false-positive biopsy recommendations, short interval follow up, and positive predictive value of biopsy recommendation. Prior to matching, women with screening ultrasound and mammography were more likely to be younger than 50 (49.7% vs 31.7%), have a family history of breast cancer (42.9% vs 15.0%), and to have dense breasts (74.3% vs 35.9%). Biopsy recommendation rate was significantly higher for women with dual screening tests (57.4 vs 27.7 per 1000 screens, RR 2.05, 95% CI 1.79 – 2.34). The false positive biopsy rate was significantly higher as well with dual screening tests (52.0 vs 22.0 per 1000 screens, RR 2.23, 95% CI 1.93 – 2.58). Positive predictive value was significantly lower with dual screening tests (9.5% vs 21.4%, RR 0.50, 95% CI 0.35 – 0.71). There was a non-significant trend towards decreased false-negative rate with dual screening tests (1.5 vs 1.9 per 1000 screens, RR 0.67, 95% CI 0.33 – 1.37). Cancer detection rate was not significantly different with dual screening tests (5.4 vs 5.5 per 1000 screens, aRR 1.14, 95% CI 0.76 – 1.68). Interval cancer detection rate was similar between both groups.
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