Breast Cancer Risk Characteristics in Women Undergoing Whole Breast Ultrasound Versus Mammography Alone
There are no consensus guidelines for complementary breast cancer screening with whole breast ultrasound. However, criteria have been identified for women at high risk for mammography screening failures (interval invasive cancer or advanced cancer).
We assessed the risk of mammography failure among women who underwent adjunctive ultrasound in clinical practice compared with women who underwent mammography alone.
A total of 38,166 screening ultrasounds and 825,360 screening mammograms without supplemental screening were identified during 2014-2020 within three Breast Cancer Surveillance Consortium (BCSC) registries. The risk of interval invasive cancer and advanced cancer was determined using BCSC prediction models.
High-interval invasive breast cancer risk was defined as heterogeneously dense breasts and 5-year BCSC breast cancer risk ≥2.5% or extremely dense breasts and 5-year BCSC breast cancer risk ≥1.67%. . Intermediate/high advanced cancer risk was defined as 6-year advanced breast cancer risk BCSC ≥0.38%.
A total of 95.3% of 38,166 ultrasounds were performed among women with heterogeneous or extremely dense breasts, compared with 41.8% of 825,360 screening mammograms without supplemental screening (p < 0.0001).
Among women with dense breasts, the risk of high-interval invasive breast cancer was prevalent in 23.7% of screening ultrasounds compared with 18.5% of screening mammograms without complementary imaging (adjusted odds ratio , 1.35; 95% CI, 1.30–1.39); intermediate/high advanced cancer risk was prevalent in 32.0% of screening ultrasounds versus 30.5% of screening mammograms without additional screening (adjusted odds ratio, 0.91; 95% CI, 0.89 –0.94).
FIGURE. BCSC invasive breast cancer risk distribution at 5 years. Among (A) all women aged 35 to 74 years and (B) women aged 35 to 74 years with dense breasts who underwent ultrasound or mammography screening alone at 32 breast imaging centers participating in the BCSC records from Vermont, San Francisco, and Chicago, 2014–2020. The BCSC 5-year invasive breast cancer risk model does not apply to women younger than 35 years or older than 74 years. Among women aged 35 to 74 years, the risk of invasive breast cancer could not be estimated because breast density was missing in 1.8% of eligible ultrasound screening exams and 0.7% of mammography screening eligible. BCSC indicates Breast Cancer Surveillance Consortium
Ultrasound screening was highly targeted at women with dense breasts , but only a modest proportion were at high risk of mammography screening failure.
A clinically significant proportion of women who underwent mammograms alone were at high risk of mammography failure.
Dense breast tissue , which contains a higher proportion of fibrous tissue than fat, is a risk factor for breast cancer and also makes it difficult to identify cancer on a mammogram. Many states have enacted laws requiring women with dense breasts to be notified after a mammogram, so they can choose to undergo supplemental ultrasound examination to improve cancer detection. A recent study published by Wiley online in CANCER , a peer-reviewed journal of the American Cancer Society, evaluated the results of such additional screening to determine its benefits and harms to patients.
Although complementary ultrasound can detect breast cancers that mammography missed, it requires additional imaging and may lead to unnecessary breast biopsies in women who do not have breast cancer. Therefore, it is important to use supplemental ultrasound only in women at high risk of mammography failure ; In other words, women who develop breast cancer after a mammogram shows no signs of malignancy.
Brian Sprague, PhD, of the University of Vermont Cancer Center, and colleagues evaluated 38,166 add-on ultrasounds and 825,360 screening mammograms without add-on ultrasounds during 2014-2020 at 32 US imaging centers within three regional registries. of the Breast Cancer Surveillance Consortium.
The team found that 95.3% of complementary ultrasounds were performed on women with dense breasts. In comparison, 41.8% of mammograms without additional screening were performed on women with dense breasts.
Among women with dense breasts, a high risk of interval invasive breast cancer was present in 23.7% of women who had ultrasounds, compared with 18.5% of women who had mammograms without additional images.
The findings indicate that ultrasound was highly targeted at women with dense breasts, but only a modest proportion of these women were at high risk of failing mammography. A similar proportion of women who only received mammograms were at high risk of mammography failure.
“Among women with dense breasts, there was very little targeting of ultrasound to women who were at highest risk of failing mammography. Rather, women with dense breasts who underwent ultrasound had similar risk profiles to women who underwent mammography alone,” Dr. Sprague said. “In other words, many women at low risk for breast cancer despite having dense breasts underwent an ultrasound, while many other women at high risk for breast cancer underwent mammography alone without additional testing.”
Doctors may consider other breast cancer risk factors beyond breast density to identify women who may be appropriate for complementary ultrasound examination. Publicly available risk calculators from the Breast Cancer Surveillance Consortium are available and also consider age, family history, and other factors (https://www.bcsc-research.org/tools).
Our results from a geographically diverse sample of breast imaging centers in the United States demonstrate that women with dense breasts predominantly used ultrasound. Other breast cancer risk factors were also more common, and the risk of mammography failure (interval invasive breast cancer and advanced cancer) was higher among ultrasound screening compared with mammography alone. Analyzes restricted to examinations among women with dense breasts indicated only modest differences in the risk of interval or advanced cancer between the ultrasound and mammography alone groups.
Overall, our findings indicate strong selection of women for ultrasound screening based solely on breast density and moderate selection based on other breast cancer risk factors, corresponding to a wide distribution in the risk of screening failure. mammography among women undergoing breast ultrasound.
The moderate differences in the risk distributions for invasive breast cancer, interval cancer, and advanced breast cancer observed in the entire study population between ultrasound screening and mammography screening alone were substantially reduced when restricted to examinations among women with dense breasts.
Notably, the prevalence of intermediate or high risk of advanced breast cancer at 6 years among women with dense breasts was higher among screening with mammography alone compared with screening with complementary ultrasound after adjusting for registration BCSC. This reinforces our conclusion that, apart from breast density, other factors associated with the risk of mammography failure, such as obesity29, are not commonly used to select women for complementary ultrasound examination.
In summary , we found that ultrasound in this geographically diverse multicenter study was strongly targeted at women with dense breasts. The distributions of breast cancer risk, interval invasive breast cancer risk, and advanced cancer risk varied widely among women who underwent ultrasound.
Many women at high risk of screening mammography failure did not undergo follow-up screening after mammography. Consideration and increased public awareness of other breast cancer risk factors beyond breast density could facilitate the identification of women at high risk for mammography screening failures who may be appropriate for ultrasound screening. complementary.
