Digital Mammography May Improve Cancer Detection

NEW YORK (Reuters Health) - As a screening measure for breast cancer, digital mammography is more accurate than conventional mammography at detecting disease in women with dense breasts, women younger than 50 years of age, and premenopausal women, new research shows.

Conventional mammography involves the creation of a breast image directly onto film. With digital mammography, by contrast, an electronic image is taken and stored in a computer. The display characteristics of the image can then be manipulated and the radiologist can use software to help detect breast abnormalities.

Previous reports have shown that conventional mammography is limited in its ability to detect cancer in dense breasts, which are commonly found in younger women, according to the report released Friday in The New England Journal of Medicine. Digital mammography was developed to address this and other limitations of conventional mammography.

Still, despite the apparent advantages for digital mammography, previous studies have failed to show that it is more accurate than conventional mammography, lead author Dr. Etta D. Pisano, from the University of North Carolina in Chapel Hill, and colleagues note. However, these studies only used one type of digital detector and did not have enough study participants to detect small differences in accuracy.

In the Digital Mammographic Imaging Screening Trial (DMIST), 49,528 women with no signs or symptoms of breast cancer were screened for the disease with both digital and conventional mammography. Two radiologists interpreted the mammograms.

Complete data were available for 86.3 percent of the study participants. Breast cancer status was determined through biopsy within 15 months of study entry or with repeat mammogram at least 15 months after study entry.

The new study compared film mammograms to digital mammograms from systems made by Fischer Imaging, Fuji Photo Film Co. Ltd., General Electric Co. and Hologic Inc. All but the Fuji system are approved by the Food and Drug Administration and available for use in the United States.

In the overall analysis, digital and film mammography were similar in their ability to identify breast cancer. As noted, however, digital mammography was significantly more accurate than film mammography at detecting cancer in women under 50 years of age, women with dense breasts, and premenopausal women.

While these findings are encouraging, the adoption of digital mammography as a routine screening measure will likely depend on another factor: cost.

"Digital systems currently cost approximately 1.5 to 4 times as much as (conventional) systems," the researchers point out. "As part of DMIST, we are performing a formal cost-effectiveness analysis."

SOURCE: The New England Journal of Medicine, September 16, 2005.