Does Better Breast Imaging Lead to Improved Outcomes or Increased Overdiagnosis?
The use of DBT appears to be associated with an increased cancer detection rate.
Highly sensitive digital breast tomosynthesis (DBT), also called 3-dimensional mammography, breast screening equipment has been rapidly adopted by mammography centers across the United States in recent years. DBT appears to be associated with an increased detection rate for preclinical breast neoplasms but adoption by imaging centers has outpaced the evidence base for this modality's utility as a screening tool. The US Preventive Services Task Force (USPSTF) has concluded that the evidence base is too small to assess its value as a primary breast screening modality, and critics voice concern that its widespread use could contribute to the overdiagnosis and overtreatment of low-risk neoplasms.
Digital breast tomosynthesis mammography is a screening and diagnostic imaging modality that more sensitively detects preclinical breast neoplasms than traditional mammography modalities.1,2
Embracing the Technology
DBT has quickly become widely available across the United States. The US Food and Drug Administration (FDA) has tracked the number of certified mammography facilities with digital breast tomosynthesis equipment since June 2016, by which time half of the facilities in the Breast Cancer Surveillance Consortium were already offering DBT screening.3As of March 2018, the most recent month for which data is available on the FDA website, there are 4074 tomosynthesis-equipped mammography centers in the United States, up nearly 30% from the 3178 recorded a year earlier, in March 2017 — and up 66% since the FDA started tracking these systems in mid 2016.4,5(In June 2016, the FDA reported 2444 DBT units at certified mammography centers.6)
Like traditional 2-dimensional mammography, DBT involves breast compression. Low-dose radiographic images of compressed breast tissue are acquired in slices, in a manner similar to computed tomography (CT), then reconstructed to produce standard mammographic views.2However, DBT resolution exceeds that of CT, allowing narrower image slice acquisition and much more detailed visualizations of breast tissue. The resulting images more sensitively depict both normal breast tissue and noncalcified breast tumors.2
DBT can involve slightly higher radiation doses than other mammography examinations and costs slightly more — approximately $50 more per examination.7,8Early studies suggest that DBT might be more sensitive than full-field digital mammography (FFDM),1and may require additional reading time compared with traditional 2D mammography images.9
DBT might prove to offer more accurate detection of early-stage malignancies and differentiation from benign neoplasms. Most DBT-detected breast cancers not detected using FFDM exhibited spiculated or indistinct margins, for example.1Spiculation is a feature of low-grade (grades 1 and 2) invasive breast malignancies that is not commonly seen in higher-grade tumors.1Spiculation is also more frequently noted in early-stage malignant neoplasms than benign growths (81% vs 11%, respectively, according to one 2010 study).10But spiculated benign neoplasms and early-stage tumors that might never progress to imperil the patient are also likely to be detected.
Critics contend that marketing pressure is driving imaging centers' widespread adoption of DBT equipment — and point out that despite its rapid and widespread adoption nationwide, its potential benefits and harms, and cost-effectiveness, remain poorly understood.7,9