Mammograms are challenging to read. Radiologists learn to read the spots and shapes that differentiate normal lumps and bumps from cancerous growths, but they acknowledge that they cannot catch all cancers. Add to that a tired, overworked and distracted physician, and the job becomes even tougher. Having a second radiologist read the mammogram catches more cancers, but only 7 percent of U.S. exams get a second reading.
Now CAD (computer-aided detection) is giving physicians that additional pair of eyes. Manufacturers and radiologists say the indefatigable computer is catching additional cancers. CAD is not perfect, but it is a valuable addition to the mammography arsenal and may someday help radiologists in the search for other cancers, such as lung and colon cancer.
CAD benefits
“From the basic and clinical research that’s been done, the technology seems to do what it was supposed to do, namely, increase the number of early breast cancers that we can detect mammographically,” says Linda Warren Burhenne, M.D., chief radiologist for the Screening Mammography Program of British Columbia and clinical professor of radiology at the University of British Columbia (Vancouver, Canada).
Three CAD systems have received FDA approval in the United States. First came R2 Technology Inc.’s (Sunnyvale, Calif.) ImageChecker in 1998, followed in 2002 by Intelligent Systems Software Inc. (ISSI of Boca Raton, Fla., and now called icad inc. (Tampa, Fla.), after a merger with Howtek Inc. (Hudson, N.H.) last June, and CADx Medical Systems Inc. (Laval, Quebec, Canada). Other companies are working on CAD systems as well. All three approved systems are about 90 percent sensitive, say their manufacturers. Each detects nearly all, about 98.5 percent, of the microcalcifications and about 85 percent of spiculated masses. Radiologists, on average, find about 80 percent of cancers on their own, statistically validating CAD’s claim that it finds more cancers.
In the most comprehensive study done to date, radiologists at the Women’s Diagnostic and Breast Health Center (Plano, Texas) tracked their CAD results for one year on nearly 13,000 women. The computer found eight cancers in addition to the 41 cancers the physicians detected without CAD, a 20 percent increase. Radiologists found nine cancers undetected by CAD.
“I don’t think there’s any question that CAD will find more cancers,” says Ronald A. Castellino, M.D., R2 Technology’s chief medical officer. “There are times when there is a finding on the image that everyone would agree is there, but even a good radiologist doesn’t see,” he says. Sometimes reading mammograms is like looking for your keys lying in plain sight. “That’s when computer-aided detection comes in. A lot of radiologists are intrigued with what CAD can do for them.”
Please refer to the December 2002 issue for the complete story. For information on article reprints, contact Martin St. Denis
