Lara C Pullen, PhD

December 04, 2014

CHICAGO — The addition of 3D mammography, or digital breast tomosynthesis, to 2D, or full-field digital, mammography can improve the detection of breast cancer, according to a new study.

"We can detect cancers that are otherwise hidden and not visible with 2D mammography," explained Per Skaane, MD, from Oslo University Hospital in Norway.

He presented results from the Oslo Tomosynthesis Screening Trial here at the Radiological Society of North America 100th Annual Meeting.

The trial was part of the Norwegian Breast Cancer Screening Program, and was conducted from November 2010 to December 2012. It is the largest prospective trial to compare 2D with 3D mammography for breast cancer screening, and involved 25,547 women.

3D mammography uses the same equipment as 2D mammography, except the x-ray tube moves in an arc across the breast. Software then reconstructs the image.

In this study, the tube on the Hologic equipment used moved in a 15 degree arc.

It takes approximately 30 seconds more per woman to capture an image with 3D than with 2D mammography, and radiologists require more time to accurately interpret the results. 3D mammography exposes the woman to approximately twice the radiation as the 2D mammography, but fewer recalls are required with 3D mammography.

The benefits of 3D mammography for breast cancer screening identified in this study confirm the findings of three prospective trials and one large retrospective trial.

Dense Breasts

In their analysis, Dr Skaane and his colleagues focused on the ability of 3D mammography to detect cancer in dense breasts. Dense breasts remain a challenge for mammography because dense tissue and cancer both appear white on mammograms, making detection difficult.

There are four categories of breast density. Only about 10% of women have category 1, or low-density, breasts, which means that the majority of women risk having a suboptimal screen with the conventional 2D mammography.

The researchers found that 3D mammography was significantly better than 2D mammography for cancer detection in women with breasts that fall into category 2, 3, or 4.

Table. Breast Malignancies Detected With Mammography

Density Category Malignancies, n 2D Mammography, n (%) 3D Mammography n (%) P Value
1 20 17 (85) 16 (80)
2 105 68 (65) 89 (85) <.05
3 and 4 132 78 (59) 106 (80) <.05

 

Transitioning to 3D

"For those of us who have used 3D mammography, it is very hard to look back at 2D," said Debra Copit, MD, from Albert Einstein Medical Center in Philadelphia.

Dr Skaane described the 3D system as a good breast screening upgrade because it leverages existing equipment, manpower, and programs.

He explained that, currently, his clinic is "the only site in Norway that is using 3D mammography for our screening." Other sites appear to be waiting for more data. "In Norway, we want harder documentation that 3D is as good as it appears to be," he explained.

There have yet to be head-to-head comparison studies of the different 3D mammography systems, he pointed out.

Hologic provided equipment and funding for the trial. Dr Skaane is a consultant with Hologic. Dr Copit has disclosed no relevant financial relationships.

Radiological Society of North America (RSNA) 100th Annual Meeting: Abstract VSBR31-16. Presented December 2, 2014.

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