Computer-aided detection (CAD) is software that helps radiologists in detection of breast cancer even in cases where no tumor was found on manually reading a mammogram. These devices were approved by the U.S. Food and Drug Administration in 1998 and have since been used widely. However a new study says computer-aided mammograms increase the risk of an unnecessary biopsy rather than spotting even minute cancers.

Funded by the National Cancer Institute, the study was carried out by researchers at the University of California at Davis. The findings appear in the April 5 issue of the New England Journal of Medicine.

Researchers report CAD was unable to find more breast cancer and caused false positive readings. Women who underwent CAD mammograms were often told to return for biopsies and other confirmatory tests. The mental trauma caused to the women would have been immense even if the biopsy turned out to be negative.

The study examined the analysis of 429,345 mammograms obtained from 1998 to 2002 at 43 mammogram facilities in the country. In the four years of the study period, seven centers switched over to computer-aided detection. This shift allowed researchers to compare the diagnosis arrived at by computer-aided detection as well as other digital methods to rule out breast cancer.

When computer-aided detection was used, 31 percent additional women were recalled for confirmatory tests to rule out breast cancer, while 20 percent had biopsies. Instead of diagnosing more breast cancer, CAD was instrumental in finding many cases of a precancerous condition called D.C.I.S., for ductal carcinoma in situ, the researchers reported.

In the seven centers that shifted to CAD in the middle of the study, the diagnosis of breast cancer did not increase. Instead DCIS was diagnosis rose to 37.4 percent from 28.1 percent in the pre-CAD days.

Overall CAD was linked to lower accuracy in diagnosing breast cancer as opposed to the time when there was no CAD. Lead researcher Dr. Joshua Fenton of the University of California, Davis felt the study was a pointer to the fact that all technology is not good.

"We would guess maybe 25 to 30 percent of facilities have adopted this, maybe more in urban centers where they have a high volume," said Fenton.

Writing in an accompanying editorial, Dr. Ferris Hall, a radiologist at Beth Israel Deaconess Medical Center in Boston said some errors could be attributed to the inexperience of the readers or radiologists. But all in all he felt the study results "constitute a substantial hit to this technology."

"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."

CAD was launched mainly to focus on possible cancerous areas that are too minute to be detected by manual interpretation of a mammogram. The software converts X-ray film into a digital file, which is analyzed by a computer and the image beamed onto the monitor.

The software pinpoints suspicious areas on the screen image, which are then reviewed by a radiologists for potential breast cancer. Earlier studies highlight possible benefits of the procedure, but the current one casts a doubt on its efficiency.

FDA says there are about 33.5 million mammography procedures performed in the United Sates annually. While it is not possible to calculate the exact number of CAD mammograms, the National Cancer Institute says 30 percent of mammography facilities have computer-aided interpretation.

The equipment required to install the software is very expensive and costs $50,000 to $175,000. But the apparent benefits convinced Medicare, which provides an extra $20 for each mammogram read with CAD. These systems are made by Hologic of Bedford, iCAD of Nashua and Kodak. If CAD were used at all mammography centers in the US it would increase costs by $550 million.

But this study says there are question marks over the effectiveness of the whole procedure in detecting breast cancer.

"This study points out the need for the use of other techniques to find cancer at its earliest stages.   NCI is incorporating techniques for imaging at the molecular level into many of its studies and is also conducting studies to improve the use of CAD and conventional mammography," said John E. Niederhuber, M.D., NCI Director.

Breast cancer is the second most common cancer in US women. The American Cancer Society estimates that in 2007 about 178,480 new cases of invasive breast cancer will be diagnosed among women in the United States and 40,460 women and 450 men will die from breast cancer in the country.

Last week the American Cancer Society recommendations called for an annual MRI exam in women at greatest risk of breast cancer.