'To do no harm,' human eyes are essential

Radiologists should not become too dependent on the use of computer-assisted detection (CAD) technology when reading screening mammograms because the doctors can see lesions that CAD sometimes misses. This is according to a study conducted at the Seattle-based Group Health Cooperative with participation from Dr. Connie Lehman, of the Seattle Cancer Care Alliance and University of Washington. The research appears in the December issue of the American Journal of Roentgenology.

"Our study shows that radiologists must continue to rely on their own judgment when determining whether lesions seen on mammograms require further testing," said Dr. Stephen Taplin, who led the research at Group Health before joining the National Cancer Institute.

CAD uses computer software to identify and mark areas of concern on mammograms. Radiologists typically review the CAD-marked images after they interpret the original film. While early CAD evaluations showed it improved cancer detection, recent studies have raised questions about CAD's performance.

The study showed that CAD assistance increased radiologists' ability to determine that a woman without cancer was, in fact, cancer free, a quality known as mammographic "specificity." Overall specificity increased from 72 percent without CAD to 75 percent with CAD. This 3 percent difference means that CAD allows 30 women in every thousand women screened to avoid further evaluation.

CAD assistance did not affect the radiologists' overall ability to spot cancer where it was present. The doctors performed equally well with and without CAD.

However, CAD does not mark all visible abnormalities. And when the researchers analyzed the radiologists' performance on mammograms with lesions that CAD did not catch, they found that the doctors were less likely to recommend further evaluation when they were using CAD than when they were not using CAD. The researchers said this means radiologists may have been relying on the CAD interpretation rather than their own interpretation, and it raises the question of whether there is a potential for CAD to do harm.