An increasingly popular technology that uses computers to scan mammograms produces worse results than human reviewers using their eyes and experience, researchers reported yesterday.
Radiologists using computer-assisted detection software were more likely to interpret a benign growth as potentially cancerous, researchers said in the New England Journal of Medicine.
The false-positive readings led to additional scans and needless biopsies, adding $550 million to the annual cost of breast cancer screening in the U.S., researchers said.
In addition, the computerized detection system, known as CAD, did not help radiologists find more real cancers, according to the report.
Dr. Ferris Hall, a radiologist at Beth Israel Deaconess Medical Center in Boston, who wrote an editorial accompanying the report, said some of the mistakes might have been owed to inexperience with CAD. It takes radiologists several years to learn the technology, he said.
Nonetheless, Hall said, the study was a setback for the technology, which is used in 30 percent of the more than 30 million mammograms performed in the U.S. annually. Many imaging centers aggressively advertise their CAD services, which are potentially more profitable than standard mammography, he said. Medicare pays an additional $20 for each mammogram screened by CAD.
"This will have a major impact on radiology," Hall said. "They were calling people back for more scans and did more biopsies - that is hurting people. And what did they get for it? No significant increase in cancer detection."
The study shows that other techniques are needed to detect breast cancer in its earliest stages, said Dr. John E. Niederhuber, director of the National Cancer Institute, which funded the study.
Breast cancer is the second-most-common cancer in women, next to skin cancer. The American Cancer Society estimates that 178,480 women will be diagnosed with the disease this year, and 40,460 will die of it.
Mammography, an X-ray image of the breast, has long been the primary tool for detecting breast cancer in its earliest stages - before tumors are large enough to detect in a clinical breast exam. Last week, the American Cancer Society recommended annual magnetic resonance imaging for women with a high risk of breast cancer.
Launched in 1998, CAD was designed to improve the accuracy of mammogram readings. A device converts the film mammogram into a digital file that can be analyzed by computer and displayed on a monitor. The software marks suspicious areas on the screen image for the radiologist to review in addition to the areas detected by the radiologist's own eyes. Each mammogram contains an average of four marks.
Previous studies assessing the benefits of the technology have produced mixed results.
The latest study looked at mammography results for 220,000 women at 43 imaging centers in Colorado, New Hampshire and Washington. Seven of the centers began using CAD during the study.
Denise Gellene writes for the Los Angeles Times.