Benefits of computer-aided screening mammography may not be enough for older women
Using computer-aided detection (CAD) software to enhance screening mammography helped identify more cases of noninvasive ductal carcinoma in situ (DCIS) in women on Medicare, but also led to more breast biopsies and other testing in the absence of breast cancer.
CAD mammography also was associated with slightly higher rates of detection of early-stage invasive breast cancer, according to lead study author Joshua J. Fenton, MD, of the University of California–Davis Health System (UC Davis) and fellow investigators. However, a longer-term study would be needed to determine whether fewer women die of breast cancer when this technology is used.
CAD has rapidly diffused into screening mammography practice despite limited and conflicting data on its clinical effect, noted Fenton's group in Annals of Internal Medicine (2013;158:580-587). “CAD is an expensive technology that has been nearly universally adopted in the United States due to Medicare's support and the hope that it can help us identify and treat invasive breast cancer early,” explained Fenton in a statement from UC Davis. “Our study suggests that we still don't know whether the benefits outweigh the harms for the average woman on Medicare.”
In their retrospective cohort study, the researchers analyzed data from 409,459 screening mammograms obtained from 163,099 women, aged 67 to 89 years, in the Medicare program (an average of 2.4 mammograms per person). They measured incident DCIS and invasive breast cancer within 1 year after mammography, invasive cancer stage, and diagnostic testing within 90 days after screening among women without breast cancer.
CAD prevalence increased from 3.6% in 2001 to 60.5% in 2006. Use of CAD was associated with a 17% greater incidence of DCIS, but with no difference in incidence of invasive breast cancer. However, among women who did have invasive cancer, CAD increased diagnoses of early-stage disease (stage I or II, as opposed to stage III or IV) by 6%.
Although CAD-driven identification of invasive breast cancer at an early stage may have benefits, DCIS is noninvasive and progresses slowly, if at all, pointed out Fenton in the UC Davis statement. “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.”
CAD also was found to increase a woman's chances of being unnecessarily called back for further imaging or other tests. Among women who were ultimately found not to have breast cancer, CAD mammography was associated with a 19% increase in additional diagnostic imaging after screening and a 10% increase in breast biopsies.