Home

  • Home
    • » e-Newsletters

In the battle between digital and analog, digital comes out on top in certain groups of women

Radiology Administrator's Compliance and Reimbursement Insider, November 1, 2005

The results of the highly anticipated Digital Mammographic Imaging Screening Trial (DMIST) are in, and digital mammography outperformed film in detecting cancers in women under age 50 and women with dense breasts.

However, it wasn't all good news for digital equipment. "[Looking at the study population as a whole] there was no significant difference between digital and film," says Etta Pisano, MD, principal investigator for the trial. This means that for the majority of women in the screening age group, there is no particular advantage to receiving a digital mammogram.

However, researchers encouraged women under the age of 50 and women with dense breasts to seek out digital mammograms, and the mainstream press widely publicized that message. This may put more pressure on your facility to purchase digital equipment if it hasn't already.

Many facilities have considered going digital but were waiting for some hard data before making the leap. This trial may give them the validation they need to make the purchase, says Pisano.

Trial background

The American College of Radiology Imaging Network conducted the study, which was designed to compare the performance of digital to film mammography. Nearly 50,000 women participated in the trial and, as part of the protocol, underwent two screening mammograms-one digital and one film.

Breast cancer was confirmed by either a biopsy within 15 months after the subject entered the trial or by a follow-up mammogram at least 10 months after study entry, according to the authors.

The trial began in 2001 and manufacturers updated digital equipment throughout the course of the trial to ensure that the most state-of-the-art equipment was used, says Pisano.

The digital advantage

Although digital imaging provided superior cancer detection only to certain groups of patients (which included perimenopausal and premenopausal women), the researchers noted that the technology had other more universal advantages, such as

  • easier access to images

  • easier use of computer-assisted diagnosis

  • improved transmission of images

  • improved retrieval and storage of images

  • lower average dose of radiation exposure for the patient while maintaining the same level of image quality

    "In a digital image, the x-ray transmission can be manipulated to enhance visualization of subtle structural changes in tissue over the entire breast," the authors wrote in the study. "For mammograms, the most problematic areas are those in which cancers can be hidden by adjacent dense tissue owing to small differences in contrast between lesions and the fibroglandular background. The visibility of a subtle mass or cluster of calcifications present in the image can be increased if the image contrast is adjusted."

    Although digital technology can detect some cancers that film misses, neither modality is able to detect all breast cancers. Therefore, it is also critical to evaluate any palpable finding detected after a negative screening mammogram, study authors wrote.

    The digital disadvantage

    However, despite the advantages of digital equipment, one main drawback exists-the cost. Digital systems typically cost about $500,000. This is one-and-a-half to four times the cost of a film system, according to the study. (Pisano says the study authors plan to complete a cost-effectiveness analysis of digital mammography soon.)

    Although reimbursement is also higher for digital procedures, some sites may not have enough volume to justify purchasing a system, says Bonnie Rush, RT(R)(M)(QM). This is true even though digital systems can also increase productivity.

    Pisano says that she hopes digital manufacturers will lower their prices in coming years. Mammography sites can help that process along by negotiating with manufacturers for price reductions, she says.

    For sites that make the digital purchase now, she says it is critical for them to try the equipment before they buy. "Make sure it is comfortable," says Pisano. "You need to test it out."

    Film is not obsolete

    Although mammography seems to be going all digital, RTs should be certain to let the public know that film equipment is still a powerful cancer detection tool, says Pisano.

    It is critical that women don't decide to skip a mammogram if they don't have access to digital equipment, says Pisano, especially because many of them may not have access to digital equipment for some time. Currently, only 8% of mammography facilities have digital equipment and until prices come down, many more may be without it for years to come.

    The study, called Diagnostic Performance of Digital versus Film Mammography for Breast-Cancer Screening, will appear in the October 27 New England Journal of Medicine and is posted on the journal's Web site at www.nejm.org .

    Insider sources

    Etta Pisano, MD, principal investigator, DMIST.

    Bonnie Rush, RT(R)(M)(QM), president of Breast Imaging Specialists, San Diego.

    Fast facts about the DMIST trial

    Name: Digital Mammographic Imaging Screening Trial

    Conducted by: American College of Radiology Imaging Network

    Purpose: To study the "small but potentially clinically important differences in diagnostic accuracy between digital and film mammography," wrote study authors.

    Enrollment: 49,528 women

    Average age of women: 54.6

    Eligibility: Women who came in for a screening mammogram at the study sites were eligible to participate unless they

  • had symptoms of breast cancer

  • had breast implants

  • thought they might be pregnant

  • had a mammogram for any reason in the past 11 months

  • had a history of breast cancer treated with a

    lumpectomy and radiation

    Ethnic backgrounds of the women in the trial:

  • White, 81.9%

  • Hispanic or Latina, 4.1%

  • Black or African American, 11%

  • Native Hawaiian or other Pacific Islander, 0.1%

  • Asian, 1.9%

  • American Indian or Alaskan Native, 0.1%

  • Other, 0.1%

    Menopausal status of women in the trial:

  • Premenopausal, 10.5%

  • Perimenopausal, 8.7%

  • Postmenopausal, 59.9%

  • Unknown or data missing, 2.3%

    Breast density of women in the trial:

  • Almost entirely fat, 10.5%

  • Scattered fibroglandular densities, 42.9%

  • Heterogeneously dense, 38.7%

  • Extremely dense, 7.5%

  • Data missing, 0.4%

    Study sites: 33 sites in the United States and Canada

    The digital equipment used: Five different types of digital equipment were used in this trial. They included the following:

  • SensoScan, Fischer Medical

  • The Computed Radiography System for Mammography, Fuji Medical

  • The Sensographe 2000D, General Electric Medical Systems

  • The Digital Mammography System, Hologic

  • Selenia Full Field Digital Mammography System, Hologic

    The process: Women underwent both a digital and film mammogram in random order. Two radiologists independently interpreted the examinations for each woman. Readers rated the mammograms using the seven-point BI-RADS malignancy scale. Breast density was also recorded using the BI-RADS scale.

    When a woman had a suspicious finding, she underwent a biopsy or aspiration of the suspicious-appearing lesion. All participants were asked to return for a follow-up mammogram after one year.

    A participant was considered to be positive for cancer if the cancer was verified within 455 days of the initial study mammogram. A participant was considered to have a negative finding if tests on a pathology report were normal or if the follow-up mammogram at one year did not show any cancer.

    Note: Because the length of time allowed for cancer detection, the sensitivities of both digital and film equipment appeared lower than sensitivities in other similar studies.

    Cancers diagnosed: During the course of the trial, 335 cancers were diagnosed. Of these cancers

  • 75.8% were diagnosed within 365 days of the study mammogram

  • 81% were diagnosed within 455 days of the study mammography

     

    • Most Popular