Better or Just More Sensitive?
Data from observational studies seem to support the efficacy of DBT in breast cancer screening.11But to date, no randomized, controlled head-to-head study has been completed to definitively compare DBT and standard mammographic imaging.1The USPSTF has concluded that the current evidence base is “insufficient to assess the benefits and harms of digital breast tomosynthesis as a primary screening method for breast cancer.”12
DBT has also arrived amid — and might well renew — a longstanding debate about screening and overdiagnosis of low-risk breast cancer.13-17Each year, approximately 60,000 US women receive diagnoses of breast screening-detected low-grade ductal carcinoma in situ (DCIS), sometimes referred to as stage 0 breast cancer.18Most undergo surgical interventions. But authors of a 2015 study of 100,000 women followed for 20 yearsconcluded that surgery for low-grade DCIS did not offer a survival benefit.17
Some experts are concerned that the improved sensitivity with DBT might contribute to overdiagnosis and overtreatment of subclinical neoplasms that are unlikely to ever pose a threat to the patient.1,7That may not be an implausible concern. New imaging technologies can contribute to such problems. For example, recent decades saw neck ultrasonography-associated overdiagnosisand overtreatment of subclinical nodules as thyroid cancers.
The US National Cancer Institute and Eastern Cooperative Oncology Group (ECOG-ACRIN) Cancer Research Group’s Tomosynthesis Mammographic Imaging Screening Trial (TMIST) is to enroll 165,000 women aged 45 to 74 years to compare DBT and conventional 2D digital mammography.
Until data from that study are available for analysis, however, the risks and benefits of DBT are likely to remain an open and contentious question.
Bryant Furlowis a medical journalist based in Albuquerque, New Mexico.
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