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Large Study on Digital Mammography Set to Begin (dateline September 10, 2001)

The largest federally-funded clinical trial on medical imaging will soon be underway to determine whether digital mammography is equal or superior to standard film mammography in helping to detect breast cancer. While the first digital mammography system has already gained U.S. Food and Drug Administration (FDA) approval and others are awaiting approval, researchers need a large-scale study to thoroughly investigate the benefits and limitations of the new technology. The study will be conducted at several locations throughout the United States.

Digital (computerized) mammography is similar to standard film mammography in that x-rays are used to produce detailed images of the breast. Digital mammography uses essentially the same mammography system as film mammography, but the digital mammography system is equipped with a digital receptor and a computer instead of a film cassette. Standard film mammography has been shown to detect approximately 85% of all breast cancers and is currently the "gold standard" in breast cancer detection. All women 40 years of age and older are recommended to have yearly screening mammograms.

Digital mammography is already being marketed directly to women and its potential benefits are exciting to breast imaging experts. However, researchers need to know whether digital mammography provides clear advantages over standard film mammography before it can be used as a widespread screening tool, according to Etta Pisano, MD, Director of Breast Imaging at the Lineberger Comprehensive Cancer Center in Chapel Hill, North Carolina. Dr. Pisano is the lead researcher for the Digital Mammographic Imaging Screening Trial (DMIST) sponsored by the National Cancer Institute.

The DMIST trial will enroll 49,500 women at 18 locations across the United States. Participants will undergo both standard and digital mammography exams. Each mammogram will require two x-ray views of each breast for a total of eight views. Some women, such as those with large breasts, may need additional views to ensure that all of their breast tissue is imaged with the digital mammography unit. Women who enroll in the clinical trial will be required to return to the same location for their annual mammogram one year after their digital and standard mammograms (or submit their mammogram films from another institution for the researchers to review). The researchers will also contact the women by phone two to three years after the trial to determine the results of their subsequent breast exams.

To date, studies of digital mammography and standard film mammography have shown that digital mammography is "comparable" to film mammography in terms of detecting breast cancer. Small studies have shown that digital mammography may provide additional benefits, such as lower radiation doses and higher sensitivity to abnormalities. For example, a study reported in the March 2001 issue of Radiology found that the use of digital mammography can lead to fewer "recalls" (repeat mammograms) than film mammography. Other data from German researchers suggest that the radiation dose can be reduced by up to 50% with digital mammography and still detect breast cancer as well as the standard radiation dose of film mammography. However, the radiation dose of standard film mammography is still extremely low and does not pose a risk to women.

From the patient’s perspective, a digital mammogram is the same as a standard mammogram in that breast compression and radiation are necessary to create clear images of the breast (however, the time it takes to perform digital mammography is typically quicker). With digital mammography, the magnification, orientation, brightness, and contrast of the mammogram image may be altered after the exam is completed to help the radiologist more clearly see certain areas of the imaged breast.

The new study will investigate several of the potential benefits of digital mammography including:

  • Improved contrast between dense and non-dense breast tissue
  • Faster image acquisition (less than a minute)
  • Shorter exam time (approximately half that of film-based mammography)
  • Easier image storage
  • Physician manipulation of breast images for more accurate detection of breast cancer
  • Ability to correct under or over-exposure of films without having to repeat mammograms
  • Transmittal of images over phone lines or a network for remote consultation with other physicians

In order to participate in the digital mammography study, women must not have a personal history of breast cancer or breast implants and must meet additional eligibility requirements. The DMIST trial will last for approximately three years, including the one-year follow-up mammogram and the two to three years of follow-up phone contact.

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