Mammo plus CAD increases cancer detection at cost of more false positives

Mammography assisted by computer-aided detection increases the detection of non-invasive and early stage invasive breast cancer, but at a cost of an increased number of false positives, according to research published in the April 16 issue of the Annals of Internal Medicine.

The study, according to Joshua Fenton, M.D., an associate professor of family and community medicine at the University of California, Davis, should stir debate about the wisdom of Medicare's investment in CAD.

"CAD is expensive technology that has been nearly universally adopted in the U.S. due to Medicare's support and the hope that it can help us identify and treat invasive breast cancer early," Fenton said. "Our study suggests that we still don't know whether the benefits outweigh the harms for the average woman on Medicare."

In the study, Fenton used U.S. Surveillance, Epidemiology and End Results (SEER) Medicare data to review the health records of more than 160,000 women between the ages of 67 and 89 who underwent 409,959 mammograms.

Of the women in the study, those screened with CAD had a 17 percent increase in diagnoses of noninvasive ductal carcinoma in situ (DCIS), and a 6 percent increase in diagnoses of early stage invasive breast cancer compared to women screened without CAD. However, among those who were screened with CAD and ended up not having breast cancer, there was a 19 percent increase in additional screening after mammography, and a 10 percent increase in biopsies.

"This means that CAD increases the chances of being unnecessarily called back for further imaging or tests because of a false alarm, which is already a major problem without CAD," study co-author Joann Elmore, a professor of internal medicine and epidemiology at the University of Washington and specialist in breast cancer screening, said in an announcement. "No woman likes receiving a notice saying that there was an abnormality on her mammogram that might or might not be cancer and more testing is necessary. This can understandably be a very stressful experience for women."

The study found that CAD was associated with higher rates of DCIS detection. But, Fenton pointed out, "DCIS progresses slowly, if at all. Some of these early noninvasive lesions may never have come to clinical attention in women's lifetimes if CAD were not applied to their mammograms."

The study also found that CAD was associated with slightly higher rates of early-stage invasive breast cancer detection. "There may be benefits if CAD detects early-stage invasive cancer before it progresses," Fenton said. "A longer-term study would be needed to see whether fewer women die of breast cancer on account of the technology."

To learn more:
- see the study abstract
- read the announcement