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Senior Citizen Health & Medicine
Computer-Aided Detection Reduces the Accuracy of
Mammograms
Women screened by CAD devices more likely to
undergo a biopsy
April 5, 2007 - Computer-Aided Detection (CAD) that
uses software designed to improve how radiologists interpret mammograms
may instead make readings less accurate, according to new research. Use
of CAD did not clearly improve the detection of breast cancer and may
have caused unnecessary biopsies.
CAD software analyzes the mammogram image and marks
suspicious areas for radiologists to review, thus assisting them in
determining which images could lead to in serious tumors. CAD was
approved by the U.S. Food and Drug Administration in 1998 and has been
incorporated into many mammography imaging practices, but its effect on
the accuracy of interpretation has been unclear.
The new research was conducted by investigators at
the University of California Davis Health System, Sacramento, Calif.,
and colleagues in the Breast Cancer Surveillance Consortium, which is
sponsored by the National Cancer Institute (NCI), part of the National
Institutes of Health.
The results of the study show that women who got
screening mammograms at centers using CAD devices were more likely to be
told their mammogram was abnormal and thus undergo a biopsy to rule out
breast cancer.
Findings appear in the April 5, 2007 issue of the
New England Journal of Medicine and were funded by NCI, the Agency for
Healthcare Research and Quality, and the American Cancer Society.
This study points out the need for the use of
other techniques to find cancer at its earliest stages. NCI is
incorporating techniques for imaging at the molecular level into many of
its studies and is also conducting studies to improve the use of CAD and
conventional mammography, said John E. Niederhuber, M.D., NCI Director.
In the end, technology facilitates screening. Ultimately, treatment
requires radiologists working with the examining physician and the
responsible surgeon to put everything together. We worry about false
positives, but we certainly dont want to miss any cancers, either.
Investigators looked at the use of screening
mammography in 222,135 women who had 429,345 mammograms. The period of
observation was from 1998 through 2002 and took place at 43 facilities
in Colorado, New Hampshire, and Washington states. The study included
2,351 women who received a diagnosis of breast cancer within one year
after screening and also received a mammogram that did or did not use
CAD.
Within three years of FDA approval, 10 percent of
the mammography facilities in the country were using CAD, said lead
researcher Joshua J. Fenton, M.D., UC Davis Health System. 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.
Seven facilities, representing 16 percent of the
study sites, implemented computer-aided detection during the study
period. With the use of CAD, 32 percent more women were recalled for
more tests and 20 percent more women had a breast biopsy. Use of the
software had no clear impact on the early detection of breast cancer.
The study suggests that, if anything, the software
may promote the detection of the least dangerous breast cancers, such as
localized, in situ breast cancers. The effect of in situ cancers on
breast cancer mortality remains unknown and some evidence suggests that
not all develop into serious cancers.
Every time the CAD software marks a real cancer, a
radiologist has to consider about 2,000 additional false-positive marks,
making it very difficult to distinguish between real cancers and those
that are not cancer. The authors estimate that for every additional
woman diagnosed with breast cancer on the basis of CAD, 156 women are
falsely recalled for more tests and 14 had unnecessary biopsies to
exclude cancer.
Its unfortunate that the use of the software has
proliferated so widely before we are certain of its benefits, said
Fenton. 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 authors estimate that if all mammography
facilities adopt CAD, the annual cost of mammograms in the United States
could increase 18 percent, or an additional $550 million nationwide.
For a Q&A on this finding, please go to
http://www.cancer.gov/newscenter/pressreleases/CADmammographyQandA.
For more information about cancer, visit
http://www.cancer.gov, or call NCI's Cancer Information Service at
1-800-4 CANCER.
The National Institutes of Health (NIH) The
Nation's Medical Research Agency includes 27 Institutes and Centers
and is a component of the U.S. Department of Health and Human Services.
It is the primary federal agency for conducting and supporting basic,
clinical and translational medical research, and it investigates the
causes, treatments, and cures for both common and rare diseases. For
more information about NIH and its programs, visit
www.nih.gov.
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