Digital breast tomosynthesis could reduce total radiation dose

NEW YORK - Replacing standard full-field digital mammography (FFDM) with two-view digital breast tomosynthesis (DBT) could cut the breast radiation dose by about half, researchers say.

Compared with FFDM, DBT has been shown to increase breast cancer detection rates by 10% to 53% and to reduce recall rates by 20% to 59%.

Despite these advantages, along with the reduction in compression and, therefore, patient discomfort, most third-party payers do not routinely cover DBT based on their conclusion that there is insufficient evidence in the medical literature to recommend it for breast cancer screening or diagnosis.

Whether breast radiation doses with DBT are within established limit recommendations has been unclear.

Dr. Tony Martin Svahn from Sydney Medical School, University of Sydney, New South Wales, Australia, and colleagues reviewed and summarized absorbed doses reported in clinical studies using DBT and FFDM and described the dose contribution from DBT relative to that from FFDM.

One-view DBT studies had estimated doses ranging from 34% to 100% of those associated with FFDM, and two-view DBT studies had estimated doses ranging from 68% to 117% of those associated with FFDM, according to the December 29 online report in The Breast.

Adding two-view DBT to FFDM resulted in estimated doses 100% to 123% higher than from FFDM alone, but replacing FFDM with synthetic 2D views reconstructed from DBT reduced the breast dose by 45%.

"While the benefit of a clinically appropriate X-ray imaging exam might outweigh the risk, efforts should nonetheless be made to minimize this risk by reducing unnecessary exposure to ionizing radiation," the researchers say. "Therefore, it is also essential to underline that optimization in breast dosimetry and other refinements in DBT technology and image reconstruction have the potential to offer additional dose savings, and are worthy of further research to ensure that adoption of DBT into routine practice is underpinned by minimization of absorbed doses to the breast."

"Ongoing and new studies of DBT in the screening setting in particular should monitor and report absorbed dose levels to inform future breast screening practice and policy," they add.

Dr. Anders Tingberg from Skane University Hospital, Malmo, Sweden, has compared digital mammography with tomosynthesis for breast cancer diagnosis. He told Reuters Health by email, "With careful optimization of the exposure parameters in tomosynthesis, the dose from a tomosynthesis examination could be the same (or even lower) as from a mammography examination. The higher sensitivity for detecting breast cancers with tomosynthesis compared to mammography, is obviously in favor for tomosynthesis."

"Careful justification is needed every time a new modality or imaging technique is to replace an old one," Dr. Tingberg said. "Do the benefits from the new modality outweigh the disadvantages associated with it? In my opinion, tomosynthesis used with optimum exposure settings could be an alternative or in some cases even replace mammography for breast cancer screening."

"One of the disadvantages of tomosynthesis, which are not discussed here, is the additional workload for the breast radiologists, that comes with the significant increase of images that need to be evaluated," Dr. Tingberg added. "This may increase the costs for tomosynthesis compared to mammography."

"Finally," he said, "this paper is about radiation dose, and only briefly mentions image quality (diagnostic quality). If a new modality gives a higher radiation dose than the previous one, but has a significantly higher diagnostic quality, then it could be justified to use the new modality anyway. This is often the case with computed tomography (CT) replacing old 2D radiography, for example."

Dr. Svahn did not respond to a request for comments.

The authors report no external funding or disclosures.


The Breast 2014.

References: Reuters Health
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