ARLINGTON, Virginia-Data from more than 40,000 women who
underwent both digital and film mammography at 33 sites in the US and Canada
show that, while the techniques have similar overall diagnostic accuracy in
breast cancer screening, digital mammography is more accurate in women under
the age of 50 years, women with radiographically dense breasts, and pre- or
Lead investigator Etta D. Pisano, MD, professor of radiology
and biomedical engineering and chief of breast imaging at the University of
North Carolina School of Medicine, Chapel Hill, presented the results of the
Digital Mammographic Imaging Screening Trial (DMIST) at the fall meeting of the
American College of Radiology Imaging Network (ACRIN).
The $26.5 million trial was funded by the National Cancer
Institute and conducted by ACRIN. Results were published in the New England
Journal of Medicine (online ahead of print on September 16, 2005).
Beginning in October 2001, DMIST enrolled 49,528 women who had no signs of
breast cancer. Women were given both digital and film mammograms, which were
interpreted independently by two different radiologists.
Breast cancer status was ascertained based on a breast
biopsy performed within 15 months of study entry or through follow-up
mammography at least 10 months after study entry. All relevant information in
accordance with study protocol was available for 42,760 women (86.3%).
Mean age of the 42,760 women with verified breast cancer
status was 54.9 years. Nearly 85% were Caucasian. Nearly two-thirds were
postmenopausal. Among these women, 14,335 were under the age of 50 years,
19,897 had heterogeneously or extremely dense breasts, and 15,803 were
premenopausal or perimenopausal. Receiver-operating-characteristic (ROC)
analysis was used to evaluate the results.
Diagnostic accuracy of digital and film mammography was
similar, with the difference between the methods in the area under the ROC
curve at 0.03 (P = .18). Key patient subsets, however, realized a
diagnostic performance benefit with digital mammography: Compared with film
mammography, the accuracy of digital mammography was significantly higher among
women under the age of 50 years (difference in AUC 0.15, P = .002);
women with heterogeneously or extremely dense breasts on mammography (AUC
difference 0.11, P = .003); and premenopausal or perimenopausal women (AUC
difference 0.15, P = .002).
Emphasizing that breast cancers detected by digital
mammography in these three patient subsets "included many invasive and
high-grade in situ cases ........precisely the lesions that must be detected
early to save lives through screening," the DMIST investigators concluded that
"the significant improvement in accuracy of specific subgroups of women
justifies use of digital mammography in these groups."