Film or Digital Mammographic Screening?
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《新英格兰医药杂志》
The report by Pisano et al.1 of the results of the Digital Mammographic Imaging Screening Trial (DMIST) in this issue of the Journal adds important information that physicians will use to assess the value of a new technique in mammographic screening: digital-image acquisition and storage. Moreover, the report by Berry et al.,2 also in this issue of the Journal, adds evidence to the already abundant data that support the role of mammographic screening in reducing breast-cancer mortality. The latter report reminds us that the technical aspects of mammography influence the quality of breast-cancer screening.
Some of the benefits of digital mammography have long been recognized by the breast-imaging community. In facilities in which all other imaging techniques are film-less, conversion to a film-less technique of mammography permits the elimination of film processing, storage, copying, and retrieval. Digital-image manipulation makes it possible to place images in a window, level them, and electronically magnify them — features that allow images to be evaluated without the need to repeat mammography. Among digital imaging's other advantages are real-time interpretation of mammograms at distant sites with the use of teleradiology and computer-aided detection equipment.
These advantages must be weighed against the cost of digital-imaging systems, which are often one and one half to four times as expensive as film-mammography systems. Women with large breasts who undergo digital mammography may require multiple exposures to ionizing radiation because the smaller image size requires the acquisition of multiple images to image the breast fully. Workstations for viewing digital mammograms are frequently not user-friendly and more time and effort are often required to read digital mammograms than film mammograms. It can also be difficult to compare digital images with older film studies. The increased expense, time, and effort have been hard for some to justify in the context of the approval of digital equipment by the Food and Drug Administration on the basis of efficacy that is only equal — not superior — to that of film mammography. It is important to recall that three previously published reports have shown film mammography to be similar to or better than digital mammography.3,4,5
The DMIST results suggest advantages of digital over film mammography in some subgroups of women, although the data for the entire population show no advantage of one technique over the other. In subgroup analyses, however, screening with digital mammography had a significant advantage among women who were younger than 50 years of age, women who were premenopausal or perimenopausal, and those with radiographically dense breast tissue on film mammography. The implication of these findings is that digital rather than film mammography should be offered to such women. Is this a reasonable conclusion, and if so, is its implementation practical?
Only about 8 percent of facilities in the United States have digital mammographic systems. The initial financial outlay for installing a digital system is considerable and can increase the expense of performing a test that currently has only a marginal cost reimbursement.
The advantage offered by digital mammography appears to be limited to a minority of the women who undergo screening. Since routine screening is recommended for women 40 years old or older, most women who undergo screening are postmenopausal and at least 50 years old, excluding them from at least two of the three subgroups that benefited from digital mammography in DMIST. The advantage of digital mammography in younger women with dense breasts was clear in DMIST, but other studies comparing digital with film mammography have arrived at different conclusions.3,4,5 In fact, a careful look at the data from DMIST suggests that in women older than 49 years, postmenopausal women, and women with less dense breasts, film mammography found more cancers than digital mammography, although the difference was not significant. This result is concordant with those of other published studies.3,4,5,6 The higher specificity of digital mammography reported in DMIST is also supported by other data.7
The diagnostic accuracy of the five types of digital systems used in DMIST was similar to that of film systems. However, some types of digital systems were used for only a small number of examinations, and therefore, the study could detect only fairly large differences between film mammography and mammography using these types of digital units. The study does not report whether certain brands of digital systems were superior to others. Thus, mammographic facilities cannot determine from DMIST whether the advantages of digital imaging identified in some subgroups apply to equipment from all manufacturers. Undoubtedly, the long-awaited results of the elegant study by Pisano et al. give us new insights into the application of digital mammography for screening. The DMIST data suggest that in facilities in which it is available, digital mammographic screening is appropriate for women in subgroups in which this approach has a demonstrated advantage over film mammography. However, in the bulk of the screening population, either technique is acceptable, and film mammography may confer a nonsignificant advantage.
Are the women who are screened at the very large number of facilities in the United States (and throughout the world) without digital mammographic systems well served? I think they are. The analysis by Berry et al., supported by data from many other studies, indicates that screening with film mammography significantly decreases breast-cancer mortality. The benefits of screening with film mammography have been shown in long-term follow-up studies with mortality as an end point, not just tumor stage, as was used in DMIST.
Expensive techniques that convey an additional advantage should be used when available. The bulk of the advantage offered by mammographic screening is independent of the type of imaging used. The lack of clear-cut data concerning the advantage (or lack of advantage) of digital units from different manufacturers also increases the difficulty of incorporating digital mammography into a screening program.
Perhaps the most important message in the work of Pisano et al. and Berry et al. is that good-quality screening mammography saves lives. The availability of high-quality images and skilled interpretation and the screening of all women who are eligible for it will yield optimal benefits. Although digital mammography can detect cancers that might be missed by film mammography, the opposite will be true for some women. All women of the appropriate age should be screened. When both types of equipment are available, the decision to use digital or film equipment should be tailored to the individual woman. If only one type of equipment is available, women should recognize that most of the benefit of mammographic screening is derived from the test itself and not from the way the image is stored.
Source Information
From the Memorial Sloan-Kettering Cancer Center, New York.
References
Pisano ED, Gatsonis C, Hendrick E, et al. Diagnostic performance of digital versus film mammography for breast-cancer screening. N Engl J Med 2005;353:1773-1783.
Berry DA, Cronin KA, Plevritis SK, et al. Effect of screening and adjuvant therapy on mortality from breast cancer. N Engl J Med 2005;353:1784-1792.
Lewin JM, Hendrick RE, D'Orsi CJ, et al. Comparison of full-field digital mammography with screen-film mammography for cancer detection rates: results of 4,945 paired examinations. Radiology 2001;218:873-880.
Lewin JM, D'Orsi CJ, Hendrick RE, et al. Clinical comparison of full-field digital mammography and screen-film mammography for detection of breast cancer. AJR Am J Roentgenol 2002;179:671-677.
Skaane P, Young K, Skjennald A. Population-based mammography screening: comparison of screen-film and full-field digital mammography with soft-copy reading -- Oslo I Study. Radiology 2003;229:877-884.
Skaane P, Skjennald A. Screen-film mammography versus full-field digital mammography with soft-copy reading: randomized trial in a population-based screening program -- the Oslo II Study. Radiology 2004;232:197-204.
Skaane P, Balleyguier C, Diekmann F, et al. Breast lesion detection and classification: comparison of screen-film mammography and full-field digital mammography with soft-copy reading -- Observer Performance Study. Radiology 2005;237:37-44.(D. David Dershaw, M.D.)
Some of the benefits of digital mammography have long been recognized by the breast-imaging community. In facilities in which all other imaging techniques are film-less, conversion to a film-less technique of mammography permits the elimination of film processing, storage, copying, and retrieval. Digital-image manipulation makes it possible to place images in a window, level them, and electronically magnify them — features that allow images to be evaluated without the need to repeat mammography. Among digital imaging's other advantages are real-time interpretation of mammograms at distant sites with the use of teleradiology and computer-aided detection equipment.
These advantages must be weighed against the cost of digital-imaging systems, which are often one and one half to four times as expensive as film-mammography systems. Women with large breasts who undergo digital mammography may require multiple exposures to ionizing radiation because the smaller image size requires the acquisition of multiple images to image the breast fully. Workstations for viewing digital mammograms are frequently not user-friendly and more time and effort are often required to read digital mammograms than film mammograms. It can also be difficult to compare digital images with older film studies. The increased expense, time, and effort have been hard for some to justify in the context of the approval of digital equipment by the Food and Drug Administration on the basis of efficacy that is only equal — not superior — to that of film mammography. It is important to recall that three previously published reports have shown film mammography to be similar to or better than digital mammography.3,4,5
The DMIST results suggest advantages of digital over film mammography in some subgroups of women, although the data for the entire population show no advantage of one technique over the other. In subgroup analyses, however, screening with digital mammography had a significant advantage among women who were younger than 50 years of age, women who were premenopausal or perimenopausal, and those with radiographically dense breast tissue on film mammography. The implication of these findings is that digital rather than film mammography should be offered to such women. Is this a reasonable conclusion, and if so, is its implementation practical?
Only about 8 percent of facilities in the United States have digital mammographic systems. The initial financial outlay for installing a digital system is considerable and can increase the expense of performing a test that currently has only a marginal cost reimbursement.
The advantage offered by digital mammography appears to be limited to a minority of the women who undergo screening. Since routine screening is recommended for women 40 years old or older, most women who undergo screening are postmenopausal and at least 50 years old, excluding them from at least two of the three subgroups that benefited from digital mammography in DMIST. The advantage of digital mammography in younger women with dense breasts was clear in DMIST, but other studies comparing digital with film mammography have arrived at different conclusions.3,4,5 In fact, a careful look at the data from DMIST suggests that in women older than 49 years, postmenopausal women, and women with less dense breasts, film mammography found more cancers than digital mammography, although the difference was not significant. This result is concordant with those of other published studies.3,4,5,6 The higher specificity of digital mammography reported in DMIST is also supported by other data.7
The diagnostic accuracy of the five types of digital systems used in DMIST was similar to that of film systems. However, some types of digital systems were used for only a small number of examinations, and therefore, the study could detect only fairly large differences between film mammography and mammography using these types of digital units. The study does not report whether certain brands of digital systems were superior to others. Thus, mammographic facilities cannot determine from DMIST whether the advantages of digital imaging identified in some subgroups apply to equipment from all manufacturers. Undoubtedly, the long-awaited results of the elegant study by Pisano et al. give us new insights into the application of digital mammography for screening. The DMIST data suggest that in facilities in which it is available, digital mammographic screening is appropriate for women in subgroups in which this approach has a demonstrated advantage over film mammography. However, in the bulk of the screening population, either technique is acceptable, and film mammography may confer a nonsignificant advantage.
Are the women who are screened at the very large number of facilities in the United States (and throughout the world) without digital mammographic systems well served? I think they are. The analysis by Berry et al., supported by data from many other studies, indicates that screening with film mammography significantly decreases breast-cancer mortality. The benefits of screening with film mammography have been shown in long-term follow-up studies with mortality as an end point, not just tumor stage, as was used in DMIST.
Expensive techniques that convey an additional advantage should be used when available. The bulk of the advantage offered by mammographic screening is independent of the type of imaging used. The lack of clear-cut data concerning the advantage (or lack of advantage) of digital units from different manufacturers also increases the difficulty of incorporating digital mammography into a screening program.
Perhaps the most important message in the work of Pisano et al. and Berry et al. is that good-quality screening mammography saves lives. The availability of high-quality images and skilled interpretation and the screening of all women who are eligible for it will yield optimal benefits. Although digital mammography can detect cancers that might be missed by film mammography, the opposite will be true for some women. All women of the appropriate age should be screened. When both types of equipment are available, the decision to use digital or film equipment should be tailored to the individual woman. If only one type of equipment is available, women should recognize that most of the benefit of mammographic screening is derived from the test itself and not from the way the image is stored.
Source Information
From the Memorial Sloan-Kettering Cancer Center, New York.
References
Pisano ED, Gatsonis C, Hendrick E, et al. Diagnostic performance of digital versus film mammography for breast-cancer screening. N Engl J Med 2005;353:1773-1783.
Berry DA, Cronin KA, Plevritis SK, et al. Effect of screening and adjuvant therapy on mortality from breast cancer. N Engl J Med 2005;353:1784-1792.
Lewin JM, Hendrick RE, D'Orsi CJ, et al. Comparison of full-field digital mammography with screen-film mammography for cancer detection rates: results of 4,945 paired examinations. Radiology 2001;218:873-880.
Lewin JM, D'Orsi CJ, Hendrick RE, et al. Clinical comparison of full-field digital mammography and screen-film mammography for detection of breast cancer. AJR Am J Roentgenol 2002;179:671-677.
Skaane P, Young K, Skjennald A. Population-based mammography screening: comparison of screen-film and full-field digital mammography with soft-copy reading -- Oslo I Study. Radiology 2003;229:877-884.
Skaane P, Skjennald A. Screen-film mammography versus full-field digital mammography with soft-copy reading: randomized trial in a population-based screening program -- the Oslo II Study. Radiology 2004;232:197-204.
Skaane P, Balleyguier C, Diekmann F, et al. Breast lesion detection and classification: comparison of screen-film mammography and full-field digital mammography with soft-copy reading -- Observer Performance Study. Radiology 2005;237:37-44.(D. David Dershaw, M.D.)