Mammography Plus Tomosynthesis Versus Mammography Alone: More Studies Needed
Digital mammography plus digital breast tomosynthesis may be more effective than digital mammography alone, but more studies are needed.
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A 44-year-old woman presents to your office for an annual visit. She has a family history of breast cancer: her mother was diagnosed at age 53. She is curious about 3-dimensional mammography and whether it would be a better screening test for her.
Digital breast tomosynthesis (DBT) is a newer imaging modality that provides a 3-dimensional reconstruction of the breast using low-dose x-ray imaging. Some studies have shown that combining DBT with digital mammography may be superior to digital mammography alone in detecting cancers.1 However, digital mammography is currently the gold standard for breast cancer screening and is the only test proven to reduce mortality.1,2
In a retrospective U.S. study of 13 medical centers,3 breast cancer detection rates increased by 41% the year after DBT was introduced, from 2.9 to 4.1 per 1,000 cases. DBT was associated with 16 fewer patients recalled for repeat imaging out of 1,000 women screened (as opposed to mammography alone). Two European studies similarly suggested an increase in cancer detection with lower recall rates.4,5
In a two-arm study by Pattacini et al,1 nearly 20,000 women ages 45 to 70 were randomized to undergo either digital mammography or digital mammography plus DBT for primary breast cancer screening. Women were enrolled over a two-year period and were followed for 4.5 years, and the development of a primary invasive cancer was the primary end point. Recall rates, reading times, and radiation doses were also compared between the two groups.
Overall, the cancer detection rate was higher in the digital mammography plus DBT arm compared with digital mammography alone (8.6 versus 4.5 per 1,000). The detection rates were higher in the combined screening group among all age subgroups, with relative risks ranging from 1.83 to 2.04 (P = .93). The recall rate was 3.5% in the two arms, with relative risks ranging from 0.93 to 1.11 (P = .52).
There was a reduction in the number of false positives seen in women undergoing digital mammography plus DBT when compared with digital mammography alone, from 30 per 1,000 to 27 per 1,000. Detection of ductal carcinoma in situ increased in the experimental arm (relative detection 2.80, 95% CI 1.01–7.65) compared with invasive cancers. Comparing radiation, the dose was 2.3 times higher in those who underwent digital mammography plus DBT. The average reading times for digital mammography alone were 20 to 85 seconds; adding DBT added 35 to 81 seconds.2
The patient should be educated on the benefits of both digital mammography alone and digital mammography plus DBT. The use of digital mammography plus DBT has been supported in various studies and has been shown to increase cancer detection rates, although data are still conflicting regarding recall rates.2, 3 More studies are needed to determine its effect on breast cancer morality.
Routine use of DBT in women with or without dense breast tissue has not been recommended by organizations such as the USPSTF and the American College of Obstetricians and Gynecologists.6,7 While there is an increased dose of radiation, it still falls below the US Food and Drug Administration limits and should not be the sole barrier to use.
Please note: This is an abridged version of an article originally published in the Cleveland Clinic Journal of Medicine.