Digital, Analogue Mammo Equal in Measuring Breast Density

Breast density can be accurately scored with images obtained through either digital mammography or film-screen (FS) mammography, according to a study published in the March issue of Radiology.

There has been a shift from FS mammography to digital, and 82 percent of mammography systems approved by the FDA are digital units. Researchers from the University of Virginia tested a hypothesis that American College of Radiology Reporting and Data System (BI-RADS) categories for breast density reporting were lower with digital mammography than with FS mammography. If this proved to be correct, adjustments would have to be made to accommodate for the different acquisition methods.

The researchers collected demographic data, risk factors, and BI-RADS breast density categories from five mammography registries that were part of the Breast Cancer Surveillance Consortium. They identified 435,751 women aged 40 or older without a history of breast cancer who underwent at least two screening mammograms less than 36 months apart between January 1, 2000, and December 31, 2009. Among this group, the sample group of 89,639 women had both digital and FS mammography and the comparison group included 259,046 women who had two FS mammograms and 87,066 women who had two digital mammograms.

The results showed that the percentage of women with a change in breast density from one reading to the next was similar, regardless of the type of mammogram. Breast density was lower in 19.8 percent of the women who underwent FS before digital mammography and 17.1 percent of those who underwent digital before FS mammography.

It was also found that lower density classifications were reported on the basis of the second mammographic examination, regardless of the acquisition method. (15.8 percent to 19.8 percent) and the percentage agreement between density readings was similar regardless of mammographic types pared (67.3 percent to 71 percent).

While there are no differences in reported BI-RADS breast density categories according to acquisition method, the authors concluded, “Reported BI-RADS density categories may be useful in the development of breast cancer risk models in which FS, digital, or both acquisition methods are used.”