Is automated whole-breast ultrasound a valid supplemental screening modality for all women with dense breasts?
Screening breast ultrasound affords us the opportunity to identify 25% more cancers that we may have missed with mammography. At a time when we are talking about overdiagnosis and ductal carcinoma in situ, it is critical to remember that the cancers we find with ultrasound are not low-grade DCIS. Rather, ultrasound detects small, largely node-negative, invasive breast cancers. The cancers we detect with screening ultrasound absolutely will become apparent. They have the potential to become, and often do become, killer cancers.
Because mammography is less effective for women with dense breasts, and because dense breasts are a strong independent risk factor for developing breast cancer, it is critical that we have a powerful tool to detect cancers that are not visible with mammography. We have an extraordinary opportunity to find early and curable breast cancers with life-saving screening breast ultrasound, and we must utilize this modality to save lives.
Screening finds cancer but also leads to benign findings that may lead to biopsy. This is the downside of screening breast ultrasound. However, the opportunity to save lives supersedes the occurrence of a false-positive, minimally invasive biopsy. At the very least, each woman should make the choice, and screening breast ultrasound should be available to all women with dense breast tissue. We certainly have more work to do to minimize the false positives with future technology. In the meantime, however, we must continue to offer women screening breast ultrasound.
The second issue with screening ultrasound is that it is very labor intensive. Automated whole-breast ultrasound harnesses this powerful tool and makes it viable in the workplace. In terms of workflow, automated whole-breast ultrasound streamlines the process, is more cost-effective and more standardized, and finds as many cancers as standard breast ultrasound. Because of the overwhelming amount of workforce needed, automation is the answer to allowing us to efficiently and effectively integrate screening ultrasound into clinical practice.
Rachel F. Brem, MD, FACR, FSBI, is director of Breast Imaging and Interventional Center, as well as professor and vice chair of the department of radiology at The George Washington Cancer Center. She can be reached at email@example.com. Disclosure: Brem reports a consultant role with Delphinus.
Women with dense breasts are at increased risk for breast cancer compared with women who do not have dense breasts, and they are more likely to have breast cancers missed by mammography. Because of this, some organizations — such as American College of Radiology — suggest that the addition of screening ultrasonography to screening mammography should be considered for women with dense breasts.
Whole-breast ultrasound as a supplement to mammography is appealing because it is widely available and uses sound waves instead of ionizing radiation. Handheld ultrasound screening (HHUS) is most frequently used but has some technical limitations, including lack of standardization of technique, image quality that is dependent on the operator holding the ultrasound probe, and longer imaging time than mammography.
The advent of automated breast ultrasound (ABUS) seeks to minimize the limitations of HHUS with standardized image acquisition using an automated transducer. ABUS allows for simultaneous visualization of breast tissue and lesions in multiple planes and batch reading of multiple examinations for efficient screening workflow. ABUS has excellent agreement with HHUS in terms of lesion visualization and cancer detection.
Some evidence suggests supplemental screening with ultrasound has the potential to improve cancer detection. However, there is limited evidence on whether supplemental ultrasound screening leads to fewer interval cancers — those diagnosed within 1 year of a negative mammographic screen — or reduces breast cancer mortality. Although clear benefit of supplemental screening has yet to be established, there is consistent evidence that adding screening ultrasound to screening mammography increases the risk for false positives, with a doubling of the number of women who are called back for additional imaging and a two- to threefold increase in biopsies that ultimately reveal no breast cancer.
Given that an estimated 28 million women in the United States have dense breast tissue, adding screening ultrasound to screening mammography among all women with dense breasts would greatly increase the harms of screening with unclear benefit.
One way to improve the benefit-harm tradeoff of supplemental screening is to focus screening on the women most likely to benefit. Rather than using ultrasound for all women with dense breasts, we believe other breast cancer risk factors should be considered in addition to breast density. Research from Breast Cancer Surveillance Consortium (BCSC), an NCI-funded research initiative, suggests that women with both dense breasts and a 2.5% chance of developing breast cancer within 5 years based on BCSC’s risk model are at highest risk for an interval breast cancer with spread to regional lymph nodes. These women are most likely to benefit from supplemental imaging beyond mammography alone. Whether actual benefit for these women can be achieved with supplemental ultrasound requires testing in a large-scale clinical trial.
At this time, until we can determine which women clearly will benefit from supplemental ultrasound screening, we do not support the use of ultrasound screening — either handheld or ABUS — for all women with dense breasts.
Janie M. Lee, MD, MSc, is associate professor of radiology at University of Washington, as well as director of breast imaging at Seattle Cancer Care Alliance. She can be reached at firstname.lastname@example.org. Diana L. Miglioretti, PhD, is professor of biostatistics at University of California, Davis, and co-leader of Breast Cancer Surveillance Consortium. She can be reached at email@example.com. Disclosure: Lee reports research funding from and a consultant role with GE Healthcare. Miglioretti reports no relevant financial disclosures.