Researchers Continue to Find Benefits to Digital Mammography (dateline April 16, 2001)
|With the U.S. Food and Drug
Administrations approval of the first full-field digital
mammography system in 2000, researchers have been investigating how digital
(computerized) mammography compares to standard film
mammography. Recent studies continue to show that digital mammography is at least as
effective as standard mammography in detecting breast cancer and may provide additional
benefits, such as lower radiation doses and higher sensitivity to abnormalities. While
full-field digital mammography is not yet widely available, physicians routinely using
digital "spot view" mammography to help guide needles during breast biopsy.
Digital mammography is similar to standard mammography in that x-rays are used to produce detailed images of the breast. Digital mammography uses essentially the same mammography system as conventional mammography, but the system is equipped with a digital receptor and a computer instead of a film cassette. The first FDA-approved full-field digital mammography system is the Senographe 2000D, made by General Electric (GE) Medical Systems. Other companies, such as Fischer Imaging Corporation, Siemens Medical Systems, and Hologic/Lorad are also developing full-field digital mammography systems that have not yet been FDA approved. Siemens Medical recently received FDA approval of its digital spot mammography module for use in making primary diagnoses of masses or calcifications. The device was originally cleared for use during stereotactic biopsy, spot localization, and for spot imaging of suspect areas.
Studies are revealing that digital mammography is equal to standard film mammography in terms of detecting breast cancer. For example, in a study published in the March 2001 issue of Radiology, John M. Lewin, MD of the University of Colorado Health Sciences and his colleagues confirmed previous findings that digital mammography detects breast cancer as well as standard x-ray mammography. However, Dr. Lewins team also found that the use of digital mammography can lead to fewer "recalls" (repeat mammograms) than film mammography.
In another study presented at European Congress of Radiology conference in March 2001, German researchers also found that digital mammography was as effective as standard film mammography in detecting abnormalities. According to lead researcher Dr. Silvia Obenauer who presented the study results, full-field digital mammography delivers consistently high image quality. Among the 100 women who received both digital and standard mammograms in the study, image contrast was found to be good in 99% of digital mammograms compared to 76% of standard film mammograms. Digital mammography also made breast skin thickening easier to see and resulted in more accurate classification of mammogram results using the American College of Radiologys BI-RADsä classification system.
Klaus Hermann and his colleagues from the University of Gottingen, Germany also found that digital mammography can achieve high quality breast images using less radiation than standard film mammography. According to Hermann, the radiation dose can be reduced by up to 50% and still detect breast cancer as well as the standard radiation dose of film mammography. However, Hermann was quick to point out that the radiation dose of standard film mammography is still extremely low and does not pose a risk to women.
The National Institutes of Health (NIH) is currently considering the approval of a 28,000 patient study on mammography. According to Laurie Fajardo, MD, professor of radiology at Johns Hopkins University School of Medicine, if approved by the NIH, this study would also investigate whether full-field digital mammography offers significant benefits over conventional film mammography, and therefore, whether the benefit of using digital mammography justifies its high cost. Digital mammography systems cost approximately four to five times as much as standard film mammography systems.
Many radiologists support digital mammography as an effective tool to screen for breast cancer. In an open letter to the FDA published in Diagnostic Imaging, Dr. Etta Pisano, Chief of Breast Imaging and Professor of Radiology at the University of North Carolina-Chapel Hill, supported the use of digital mammography. "We believe that digital mammography has advantages over standard screen-film mammography that are readily apparent from the study of phantom images and the physical parameters that can be measured. The contrast resolution of these devices is inherently better," said Dr. Pisano.
Other benefits of digital mammography include:
Disadvantages of digital mammography include:
While researchers continue to investigate the pros and cons of digital mammography, standard film mammography is still used at most mammography facilities. Film based mammography detects approximately 85% of all breast cancers and is considered the gold standard in breast cancer detection. In a comprehensive review of breast cancer detection methods, the Institute of Medicine (IOM) recently reported that standard film mammography is still the best available method to detect breast cancer. The IOM found that mammography contributed to a 2% annual decline in breast cancer deaths in the past 10 years. However, they still recommend that further research investigate better methods of breast cancer detection.
According to the American Cancer Society and other organizations, all women should begin receiving annual screening mammograms at age 40. Women over 40 should also receive annual physician-performed clinical breast exams and practice monthly breast-self exams. Screening mammograms are not usually recommended for women younger than 40 unless they are at high risk for breast cancer, as determined by their physician. However, women under 40 should still receive clinical breast exams and practice monthly breast self-exams.