ACRIN Announces DMIST Results


Certain Groups May Benefit from Digital Mammograms

Excitement was palpable at the September fall meeting of the American College of Radiology Imaging Network (ACRIN), held at the Ritz-Carlton in Pentagon City, Va. Results of the Digital Mammographic Imaging Screening Trial (DMIST) were about to be announced to the 320 attendees at the Friday morning plenary session. Etta Pisano, MD, the study's principal investigator, approached the podium and shared the findings with the audience of radiologists, research associates, patient advocates, and the news media.

Dr Pisano explained that the results from DMIST, a large clinical trial of digital versus film mammography, showed certain groups may benefit significantly from digital mammograms:

  • women with dense breasts
  • women who are premenopausal or perimenopausal
  • women who are younger than age 50

For the general population of women, digital and film mammography were equally effective.

Digital mammography takes an electronic image of the breast and stores it directly in a computer, allowing the recorded data to be enhanced, magnified, manipulated for further evaluation, and even printed on film.

This allows radiologists to use software to further interpret the mammograms. Film mammography units use film to both capture and display the image. The sensitivity of film mammography is somewhat limited in women with dense breasts—a population with a higher risk for breast cancer. One limitation of film mammography is that once the film is taken, it cannot be significantly altered; if the film is underexposed, for example, contrast is lost and cannot be regained.

Dr Pisano held a press conference on September 16, to discuss the study's findings with the news media. An article by Dr Pisano et al, titled, "Diagnostic Performance of Digital vs Film Mammography for Breast Cancer Screening – The Results of the American College of Radiology Imaging Network (ACRIN) Digital Mammographic Imaging Screening Trial (DMIST)" was published that same day in a special online edition of the New England Journal of Medicine (www.nejm.org).

The primary aim of DMIST was to compare the diagnostic accuracy of digital mammography to the diagnostic accuracy of film mammography for the purpose of breast cancer screening. Starting in October 2001, DMIST enrolled 49,528 women at 33 sites in the United States and Canada who were asymptomatic for breast cancer. All participants underwent both digital and film mammography in random order. Mammograms were interpreted independently by 2 certified 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.

The study was conducted by ACRIN, a National Cancer Institute-sponsored clinical trials cooperative group made up of investigators from over 100 academic and community-based facilities in the United States, as well as several abroad. Five digital mammography systems were used: the SenoScan (Fischer Medical), the Computed Radiography System for Mammography (Fuji Medical), the Senographe 2000D (General Electric Medical Systems), the Digital Mammography System (Hologic), and the Selenia Full Field Digital Mammography System (Hologic). The diagnostic accuracy of digital mammography did not vary significantly by machine type.

The study found that in the entire population, the diagnostic accuracy of digital and film mammography was similar. However, the accuracy of digital mammography was significantly higher than that of film mammography among women under 50, women with heterogeneously dense or extremely dense breasts, and premenopausal or perimenopausal women. The histologic findings and the stage of the breast cancers detected by the 2 methods were similar. The diagnostic accuracy of digital mammography did not vary significantly from film mammography according to race or the risk of breast cancer.

The authors wrote that, in addition to the differences the study found between digital and film mammography, "Digital mammography offers other advantages over film mammography—namely, easier access to images and computer-assisted diagnosis; improved means of transmission, retrieval, and storage of images; and the use of a lower average dose of radiation without a compromise in diagnostic accuracy. We believe that the significant improvement in accuracy in specific subgroups of women justifies the use of digital mammography in these groups." At present, however, only 8% of the mammography units in the United States are digital systems, whereas approximately 40% of women undergoing screening mammography have dense breasts. (See sidebar on page 8 for the ACR's statement about screening.)

The authors note, "One of the major impediments to the adoption of digital mammography will be its cost: digital systems currently cost approximately 1.5 to 4 times as much as film systems." Secondary goals measuring the relative cost-effectiveness of both digital and film technologies and the effect on participant quality of life due to the expected reduction of false positives are still being assessed and will be reported later.

Dr Pisano, Kenan Professor of Radiology and Biomedical Engineering at the University of North Carolina (UNC) at Chapel Hill and director of the Biomedical Research Imaging Center at the UNC, says of the findings, "These results will give clinicians better guidance and greater choice in deciding which women would benefit most from various forms of mammography."

Breast cancer has a very similar appearance in digital and film mammograms, but the display of the images on monitors instead of film will require additional reader (radiologist) training, according to the Mammography Quality Standards Act, the federal law governing mammography.

According to the National Cancer Institute, breast cancer is the most common non-skin cancer in the United States and the second leading cause of cancer-related death in women. An estimated 211,240 women will be diagnosed with breast cancer and an estimated 40,410 women will die of the disease in the United States in 2005.

Bruce Hillman, MD, network chair of ACRIN, stated, "I am very proud of the accomplishments of the DMIST researchers. The DMIST team of clinicians and scientists did a truly miraculous job in completing this complex trial quickly and producing these important results. This landmark trial, along with others currently being conducted by ACRIN, will influence the appropriate care of women everywhere."

To learn more about ACRIN protocols, visit www.acrin.org.

Left, digital mammogram and right, film mammogram, of the same breast from the same patient.