Radiologists continue to look for ways to improve the identification of early breast cancers. One recent trial revealed that magnetic resonance imaging (MRI) can detect abnormalities that mammography and clinical examination miss in some women.
In a multicenter trial of 969 women recently diagnosed with unilateral breast cancer, MRI detected cancer missed by mammography and clinical exam in 3% of the contralateral breasts. Positive MRI results led to 121 biopsies and the discovery of 30 early-stage cancers, 60% of which were invasive carcinomas. Study coauthor Etta Pisano told AJN that mammography screening of the general population finds four to seven cancers per 1,000-far fewer than the three in 100 detected with MRI in this study. Using MRI to detect cancer in the opposite breast when patients are first diagnosed with unilateral breast cancer would allow both cancers to be treated simultaneously. In addition, breast MRI's negative predictive value of 99% could reduce the number of unnecessary prophylactic mastectomies of the contralateral breast, the authors suggest.
The researchers point out that the "increased rate of detection of cancer comes with a false positive rate of 10.9%," but "this imaging tool appears to improve the detection of cancer in women at increased risk, such as women with a recent diagnosis of breast cancer." Breast MRI is being suggested for other women as well. In March the American Cancer Society (ACS) recommended that most high-risk women-those with at least a 20% to 25% lifetime risk of breast cancer-have both breast MRI and a mammogram annually beginning at age 30 to improve the early identification of cancers. Read the updated ACS breast screening guidelines at http://caonline.amcancersoc.org/cgi/content/full/57/2/75.
Using computer-aided detection software, designed to assist radiologists by highlighting suspicious areas on a mammogram, in contrast, does not improve cancer detection, according to a recent study. Researchers evaluated more than 429,000 routine mammograms from 222,135 women with no breast cancer history. Mammography centers that used computer-aided detection software had "significantly lower overall accuracy" than those that did not. Moreover, use of the software increased the rate of false positive results and "patient callbacks," as well as increasing biopsies by 20%. Detection of invasive breast cancer decreased by 12%, but identification of ductal carcinoma in situ increased by 34%.
The authors estimate that using the software would identify one additional case of cancer-most likely a ductal carcinoma in situ-for every 157 women recalled for follow-up imaging for suspicious findings and every 15 biopsied. That would add approximately $550 million to the national cost of mammography screening. The authors write that "larger studies are needed to judge more precisely whether benefits of routine use of computer-aided detection outweigh its harms."
Carol Potera