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 perimenopausal women.
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."