Drawbacks of Adding MRI to Mammography Plus Ultrasound May Outweigh BenefitsAdding ultrasound or magnetic resonance imaging (MRI) to annual screening mammograms for women with an increased risk of breast cancer and dense breast tissue detects more new breast cancers than mammography alone but also results in more false-positive findings, according to results of a multicenter clinical trial. Findings from the ACRIN 6666 trial, which was co-sponsored by NCI’s Cancer Imaging Program and the Avon Foundation for Women, will be published April 4 in JAMA.
More than 2,800 women with dense breasts and at least one other risk factor for breast cancer, such as a personal history of breast cancer, consented to undergo three annual screens with mammography plus ultrasound. After three rounds of screening, 703 women underwent an MRI. Complete data were available for 612 of these women.
Researchers found that adding ultrasound to mammography increased breast cancer detection by an average of 3.7 cases per 1,000 women screened after the second and third rounds of annual screening. The majority of cancers detected only by ultrasound were node-negative invasive cancers. Until now, it had been unclear whether continuing annual ultrasound screening would detect more cancers.
Although the risk of false-positive results with annual screening ultrasound was lower in the second and third screens than in the first screen, the addition of ultrasound led to an increased rate of biopsies, with about 5 percent of women in the second and third screening rounds having a biopsy—only 7.4 percent of which revealed cancer.
Adding a single MRI further increased cancer detection to a rate of 14.7 cases per 1,000 women screened. Of the women screened with MRI, 7 percent had a biopsy only because of the MRI, of whom 19 percent were found to have cancer. The number of screens needed to detect one cancer was 127 for mammography, 234 for supplemental ultrasound, and 68 for supplemental MRI.
Although MRI was better at detecting cancer than mammography plus ultrasound, women found it less tolerable. The authors also noted that the rate of cancers found between screenings because of a palpable lump or other breast change was low and that all of these cancers were node negative at diagnosis. Thus, they said, “it is unclear that the added cost and reduced tolerability of screening MRI are justified in women at intermediate risk for breast cancer in lieu of supplemental screening with ultrasound.”
“Despite its higher sensitivity, the addition of screening MRI rather than ultrasound to mammography in broader populations of women at intermediate risk with dense breasts may not be appropriate, particularly when the current high false-positive rates, cost, and reduced tolerability of MRI are considered,” the authors concluded.
See also: “Mammography Plus Breast Ultrasound Yields Mixed Results”