Digital mammography may benefit some women
Digital mammography may benefit some women
Clinicians who are weighing use of digital vs. film mammography for detection of breast cancer may be able to make more informed choices now that results of a large national study have been compiled.1 Results from the Digital Mammographic Imaging Screening Trial (DMIST) indicate that women with dense breasts, who are pre- or perimenopausal, or who are younger than age 50 may benefit most from having a digital mammogram. Researchers classify premenopausal women as those who had had their last menstrual period less than one month before mammography; perimenopausal women have had their last menstrual period at least one month but fewer than 12 months before mammography.1
Clinicians need powerful diagnostic tools to battle breast cancer, the most frequently diagnosed cancer (excluding cancers of the skin) in U.S. women.2 The American Cancer Society in Atlanta estimates some 211,240 cases of invasive breast cancer will be diagnosed in 2005, with 40,410 deaths expected in the same time period.2
Standard film mammography has been effectively used for more than 35 years; however, it is less sensitive for women who have dense breasts. Prior studies have suggested that approximately 10%-20% of breast cancers that were detected by breast self-examination or physical examination are not visible on film mammography.3,4 The film used in the traditional diagnostic test presents its own limitations; for example, if a film image is underexposed, image contrast is lost and cannot be regained.
Digital mammography employs computer technology to capture an electronic image of the breast. Specialists then can enhance, magnify, or manipulate the images for further evaluation. About 8% of breast imaging units in the United States provide digital mammography, according to the National Cancer Institute (NCI), which sponsored the DMIST trial.
DMIST researchers found that the cancers detected by digital mammography and missed by film mammography included many invasive and high-grade in situ cases — precisely the kinds of cancers needed to be detected early to save lives.1
"The groups of women who may benefit from digital technology are those in which standard mammography has been less effective," says the study’s lead author, Etta Pisano, MD, professor of radiology and biomedical engineering at the University of North Carolina at Chapel Hill (UNC-CH) and director of UNC-CH’s Biomedical Research Imaging Center. "These results will give clinicians better guidance and greater choice in deciding which women would benefit most from various forms of mammography."
Review the study
To conduct the DMIST trial, investigators recruited some 49,500 women at 33 sites in the United States and Canada. Women participating in the study had no breast cancer symptoms and agreed to undergo a follow-up mammogram at the same participating site or provide their mammograms from another institution for review one year from study entry. Study participants were given digital and film examinations, which were interpreted independently by two radiologists. Breast cancer status was determined through available breast biopsy information within 15 months of study entry or through follow-up mammography 10 months or later after study entry.
Four digital mammography systems (General Electric Medical Systems, Fuji Medical Systems, Fischer Imaging, and Hologic) were tested in the trial. Of these, all except for the Fuji system are approved by the Food and Drug Administration and are available for clinical use in the United States, according to NCI.
When looking at the entire population of women studied, digital and film mammography had very similar screening accuracy, DMIST findings indicate. Based on the results of the studies, investigators determined there is no apparent benefit of digital over film mammography for women who fit all of the following three categories:
- those older than age 50;
- those who do not have dense or heterogeneously (very dense) breast tissue;
- those who are not still menstruating.
Money may play a factor when it comes to which diagnostic platform is used for mammography. Current Medicare reimbursement for digital screening mammography is $135.29, compared to $85.65 for film-screen mammograms.5 Data on the relative cost-effectiveness of digital and film technologies have been compiled and will be reported at a later date, says Daniel Sullivan, MD, associate director of NCI’s division of cancer treatment and diagnosis.
Regardless of the platform used, women should continue to have regular mammograms for breast detection. According to the NCI, women in their 40s should be screened every one to two years with mammography, and women ages 50 and older also should be screened every one to two years.5 Women who are at higher than average risk of breast cancer are advised to talk with their clinicians whether they should begin screening before age 40.5
References
- Pisano ED, Gatsonis C, Hendrick E, et al. Diagnostic performance of digital versus film mammography for breast-cancer screening. N Engl J Med 2005 Sep 16; [Epub ahead of print]. Accessed at: content.nejm.org/cgi/content/abstract/NEJMoa052911v1.
- American Cancer Society. Breast Cancer Facts & Figures 2005-2006. Atlanta; 2005.
- Carney PA, Miglioretti DL, Yankaskas BC, et al. Individual and combined effects of age, breast density, and hormone replacement therapy use on the accuracy of screening mammography. Ann Intern Med 2003; 138:168-175. [Erratum, Ann Intern Med 2003; 138:771.]
- Kerlikowske K, Grady D, Barclay J, et al. Effect of age, breast density, and family history on the sensitivity of first screening mammography. JAMA 1996; 276:33-38.
- National Cancer Institute. Digital vs. Film Mammography in the Digital Mammographic Imaging Screening Trial (DMIST): Questions and Answers. Accessed at: www.nci.nih.gov/newscenter/pressreleases/DMISTQandA/print?page=&keyword=.
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