CHICAGOComputer-aided detection (CAD) is proving to
be a technologic leap in the identification of breast tumors with subtle
findings on mammography that can easily be missed by the radiologist, said
Timothy W. Freer, MD, director of the Women’s Diagnostic and Breast Health
Center, Plano, Texas.
In the largest clinical study of the technology to date, Dr.
Freer and his associates found that CAD improved the detection of breast cancer
"There has been no other modality or new technology or
method for the early detection of breast cancer that has increased our
detection rate by 20% at one time," he said at the 86th Annual Meeting of
the Radiological Society of North America (RSNA).
The study included 12,860 women who underwent standard
screening mammography at the Plano center. The mammograms were initially
interpreted by one of two experienced breast radiologists without knowledge of
the CAD analysis, followed immediately by reevaluation of the CAD-prompted
The screening uncovered 49 unsuspected breast cancers: 32 of
these cancers were recognized by both CAD and the radiologist; 9 were found by
the radiologist alone; and 8 were spotted only with the help of CAD, Dr. Freer
reported. Thus, CAD increased the number of breast cancers detected from 41 to
49, an increase of 20%.
CAD also increased the proportion of early-stage breast cancers
(stage 0 and I). Of the 41 malignancies detected by the radiologists without
CAD, 30 were early stage (73%). With CAD, an additional 8 cancers were
detected, all of which were early stage (38 of 49, 78%).
CAD did not, however, cause radiologists to call back an
excessive number of women for further evaluation of breast screening results.
The recall rate rose from 6.5% to 7.7%, which is within acceptable limits and
in proportion with the 20% increase in the rate of detection of breast cancers.
Nor did CAD excessively increase the number of women undergoing
unnecessary breast biopsies. The positive predictive value (38%) did not change
whether or not CAD was employed.
The Women’s Diagnostic and Breast Health Center has been
prospectively analyzing CAD results since the first system (ImageChecker) was
approved by the US Food and Drug Administration in 1998.
This system converts a standard mammographic film image into a
digital image that can be scanned according to a computerized algorithm
programmed to look for subtle signs of breast malignancy. CAD then displays an
image to the radiologist that contains small marks, or prompts, on areas of
breast tissue with suspicious, possibly malignant patterns of presentation.
Dr. Freer acknowledged that more extensive study is needed to
determine whether the experience at the Women’s Diagnostic and Breast Health
Center can be duplicated in other imaging centers around the country.
"We are very excited about this technology, and we have
great hopes that this study will help facilitate the initiation of a much
larger, multi-institutional study in the future."