Adding 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.

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 MRI was better at detecting cancer than mammography plus ultrasound, women found it less tolerable. “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.

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