Technology Can't Replace Doctors' Judgment in Reading Mammograms
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 Group Health Cooperative, a Seattle based health care system. 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 Stephen Taplin, MD, MPH, who led the research at Group Health before joining the National Cancer Institute as a senior scientist.
Computer-assisted detection 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, more recent studies have raised questions about CAD's performance. For example, while it is believed that CAD alerts radiologists to potential areas of concern, experts have wondered whether CAD too frequently marks normal areas rather than only identifying problem areas that the radiologist should have detected.
To answer these questions, the researchers at Group Health designed a study using a sample from more than 56,000 screening mammograms taken between 1996 and 1998. By identifying cases of breast cancer diagnosed within two years after the mammograms were taken, they created a total set of 441 mammograms from three different groups. Included were mammograms from women who:
1) remained cancer-free two years after their mammograms
2) developed breast cancer within one year, or
3) developed breast cancer within 13 months to two years.
The sample was then used to test the performance of 19 radiologists, each of whom read 341 mammograms with and without CAD. The researchers then compared the results of the two approaches for each mammogram.
This is the first study of CAD using a random sample of cases from a screened population rather than using selected cases of visible cancers. In this way, it more closely resembles the way that radiologists use CAD in real practice.
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