Digital mammography may improve cancer detection
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.
Stages of Breast Cancer (from the American Joint Committee on Cancer):
- STAGE 0. In Situ (“in place”) disease in which the cancerous cells are in their original location within normal breast tissue. Known as either DCIS (ductoral carcinoma in situ) or LCIS (lobular carcinoma in situ) depending on the type of cells involved and the location, this is a pre-cancerous condition, and only a small percentage of DCIS tumors pregress to become invasive cancers. There is some controversy within the medical community on how to best treat DCIS.
- STAGE I. Tumor less than 2 cm in diameter with no spread beyond the breast
- STAGE IIA. Tumor 2 to 5 cm in size without spread to axillary (armpit) lymph nodes or tumor less than 2 cm in size with spread to axillary lymph nodes
- STAGE IIB. Tumor greater than 5 cm in size without spread to axillary lymph nodes or tumor 2 to 5 cm in size with spread to axillary lymph nodes
- STAGE IIIA. Tumor smaller than 5 cm in size with spread to axillary lymph nodes which are attached to each other or to other structures, or tumor larger than 5 cm in size with spread to axillary lymph nodes
- STAGE IIIB. The tumor has penetrated outside the breast to the skin of the breast or of the chest wall or has spread to lymph nodes inside the chest wall along the sternum
- STAGE IV. A tumor of any size with spread beyond the region of the breast and chest wall, such as to liver, bone, or lungs
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.
Revision date: July 4, 2011
Last revised: by Dave R. Roger, M.D.