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What is DMIST?

What is DMIST?
Who was eligible to join?
Why is this study needed?
How long will the trial last?
What happened during the study?
What is a digital mammogram like?
How is digital mammography different from film mammography?
Why was DMIST important?
Who organized the study and how much did it cost?
Which digital mammography equipment was included in DMIST?
How important is reader training in interpreting digital mammography?

What is DMIST?

The purpose of this study is to find out whether digital mammography is as good as, or better than, conventional screen-film mammography. Digital mammography takes an electronic image of the breast and stores it directly in a computer allowing the recorded data to be enhanced, magnified, or manipulated for further evaluation. The electronic image also can be printed on film. Images taken with conventional screen-film mammography units only can be printed on film.

The American College of Radiology Imaging Network (ACRIN) coordinated the study and announced on Nov. 14, 2003, that DMIST had reached its target 49,500 participant recruitment goal. The trial is now closed to further enrollment while researchers analyze the data.

Radiologists participating in the research project now will use the DMIST data and images to carry out studies related to the diagnostic accuracy of both digital and conventional mammography. In addition, DMIST researchers will measure the relative cost-effectiveness of both technologies and their effect on patient quality of life.

The first DMIST study results were released by ACRIN on Sept. 16, 2005 (see the press release) and published in a special online edition of the New England Journal of Medicine that day.

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Who was eligible to join DMIST?

Women who:

  • presented for screening mammography at their normal screening interval,
  • 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,
  • did not have a focal dominant lump or a bloody or clear nipple discharge,
  • did not have a history of breast cancer treated with lumpectomy,
  • did not have breast implants,
  • were not pregnant,
  • reviewed and signed the study consent form.

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Why is this study needed?

The aim of the DMIST study is to discover whether digital mammography is able to detect breast cancer more accurately than conventional screen-film mammography.

Digital mammography may offer advantages over conventional mammography because:

  • The images can be stored and retrieved electronically, which makes long-distance consultations with other mammography specialists easier.
  • The images can be adjusted by the radiologist, and subtle differences between tissues may be noted.
  • Digital mammography may reduce the number of necessary follow-up procedures.

The DMIST study is needed because, although digital mammography has many advantages, so far there is no evidence to show that digital images are more helpful in finding cancer than conventional screen-film images.

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How long will the trial last?

The trial is now closed. All women enrolled in the study got their usual mammogram and also a digital mammogram during the same appointment at a DMIST site when they enrolled in the trial. Women were asked to return to the same DMIST site one year later for their follow-up mammogram. Some women may also have been contacted by telephone or mail up to three years later to see if they had had normal mammograms and breast examinations.

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What happened during the study?

Women who joined DMIST:

  • had both a screen-film and a digital mammography examination. On the appointment day, participants:
    • reviewed and signed the study-specific consent form,
    • were asked to provide background information about themselves and to fill out some brief questionnaires,
    • had a standard screen-film mammogram taken (a minimum of two views per breast),
    • had a digital mammogram taken (a minimum of two views per breast).
  • Each examination was interpreted independently by a board-certified radiologist with special expertise in mammography. The same certified radiologist interpreted both the conventional and digital mammogram exams.
  • Participants were asked to return in one year for their annual mammogram. At that time, a screening mammogram was taken as would be performed as part of routine health care. Women who were not able to return to the same site in one year were requested to submit films from another institution for review.
  • Participants may also have been contacted by telephone up to three years after their exam to see if they had had normal mammograms and clinical breast exams.
  • For some women, especially those with large breasts, additional digital and screen-film mammograms may have been taken to assure that all portions of the breast were included.

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What is a digital mammogram like?

From the patient's perspective, a digital mammography examination is similar to the traditional mammography examination. Positioning and compression of the breast are identical.

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How is digital mammography different from film mammography?

Both digital and film mammography use X-rays to produce an image of the breast.

In film mammography, which has been used for over 35 years, the image is created directly on a film. While standard film mammography is very good, it is less sensitive for women who have dense breasts. Prior studies have suggested that approximately 10 percent to 20 percent of breast cancers that were detected by breast self-examination or physical examination are not visible on film mammography. A major limitation of film mammography is the film itself. Once a film mammogram is obtained, it cannot be significantly altered; if the film is underexposed, for example, contrast is lost and cannot be regained.

Digital mammography takes an electronic image of the breast and stores it directly in a computer. Digital mammography uses less radiation than film mammography. Digital mammography allows improvement in image storage and transmission because images can be stored and sent electronically. Radiologists can also use software to help interpret digital mammograms. One of the obstacles to greater use of digital mammography is its cost, with digital systems currently costing approximately 1.5 to 4 times more expensive than film systems.

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Why was DMIST important?

Breast cancer is the most common non-skin cancer, and the second leading cause of cancer-related death in women in the United States. Death rates from breast cancer have been declining since 1990 and these decreases are believed to be the result, in part, of earlier detection and improved treatment.

DMIST was performed to measure relatively small, but potentially clinically important, differences in diagnostic accuracy between digital and film mammography. While any differences that were detected might be relatively small, they could improve breast cancer detection for all or some groups of women.

Digital mammography is a newer technology that is becoming more common. Currently, approximately 8 percent of breast imaging units provide digital mammography. Past trials of digital mammography have shown no difference in diagnostic accuracy between digital and film mammography. The U.S. Food and Drug Administration (FDA) trials and three smaller screening trials showed no significant difference in the performance of digital mammography vs. film mammography. These studies were limited, however, because they each included only one type of digital detector and had relatively small numbers of patients, perhaps limiting their ability to detect small differences in diagnostic accuracy.

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Who organized the study and how much did it cost?

The American College of Radiology Imaging Network (ACRIN) coordinated the study. ACRIN is a Cooperative Group sponsored by the Division of Cancer Diagnosis and Treatment, NCI. Enrollment began in October 2001. On Nov. 14, 2003, DMIST reached its targeted 49,500 participant recruitment goal. ACRIN is a National Cancer Institute (NCI)-sponsored network of physicians, scientists, and medical institutions that have joined together to conduct clinical trials of new medical imaging technologies. The total cost of the digital mammography trial was about $26 million.

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Which digital mammography equipment was included in DMIST?

General Electric Medical Systems, Fuji Medical Systems, Fischer Imaging, and Hologic digital mammography systems were tested in the trial. Of these, all except for the Fuji system are already FDA-approved and available for clinical use in the U.S.

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How important is reader training in interpreting digital mammography?

Breast cancer has a very similar appearance on digital and film mammograms, but the display of the images on monitors instead of film requires additional reader (radiologist) training. Under the federal law that governs mammography in the U.S. (the Mammography Quality Standards Act), radiologists who switch from interpreting film to interpreting digital mammography must undergo some minimal additional training.

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  • Updated: September 16, 2005