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Large Study Casts Doubt on Value of CAD

Large Study Casts Doubt on Value of CAD

SACRAMENTO, California—Computer software used to help decipher screening mammograms reduces interpretation accuracy, increases the rate of unnecessary biopsies, and offers no clear improvement in the detection of invasive breast cancer, the largest and most comprehensive community-based study of the technology has found.

Researchers examined the use of computer-aided detection (CAD) in interpreting routine mammograms as part of a survey of 43 facilities in Colorado, New Hampshire, and Washington. The study, which ran from 1998 to 2002, included 429,345 mammograms from 222,135 women, and 2,351 patients who received a breast cancer diagnosis within 1 year after screening. The results showed that women screened at facilities using CAD were more likely to be told their mammograms showed abnormalities, which resulted in an increased number of biopsies (N Engl J Med 356:1399-1409, 2007).

CAD software marks suspicious areas on a mammogram for further review by radiologists, with the intent of aiding the detection of potential or actual invasive tumors. FDA approved CAD software for interpreting mammograms in 1998, and many medical imaging practices now have incorporated the technique for use by their radiologists. Indeed, according to Joshua J. Fenton, MD, the study's lead author, 10% of US mammography facilities adopted the technology within 3 years of its approval.

"There had been no large-scale community-based review of CAD efficacy despite the rapid adoption of this technology, so we did this study to see if CAD was proving to be beneficial," said Dr. Fenton, assistant professor of family and community medicine, University of California, Davis. "It's unfortunate that the use of the software has proliferated so widely before we are certain of its benefits. We need studies to determine if the benefits of the software outweigh its harms and costs. There is also the potential for new studies to improve the performance of CAD software."

The study was conducted by researchers at the University of California Davis Health System, Sacramento, and the Breast Cancer Surveillance Consortium, an NCI-supported effort to assist research by linking mammogram registries to population-based cancer registries. All the facilities surveyed contributed data to consortium registries. The study measured things that can affect mammogram interpretation, such as procedures used in reading the images, use of CAD, and a radiologist's years of experience and the number of mammograms interpreted in the previous year.

Key Findings

During the 5-year survey, seven (16%) of the facilities began using CAD and served as the study's comparison group. The team tracked newly diagnosed invasive breast cancers and ductal carcinomas in situ through the end of 2003. Key findings include:

• Diagnostic specificity dropped from 90.2% prior to the use of CAD to 87.2% after the incorporation of CAD into the interpretation process (P < .001).

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