Abbreviated Breast MRI May Outperform Digital Breast Tomosynthesis for Detecting Cancer in Dense Breasts

By Will Boggs MD

February 27, 2020

NEW YORK (Reuters Health) - Compared with digital breast tomosynthesis (DBT), abbreviated breast MRI is associated with a significantly higher rate of detection of invasive breast cancer among women with dense breasts undergoing screening, researchers report.

"Women with dense breasts are underserved by radiographic screening . . . because the dense tissue can mask existing cancer (and is also associated with an increased risk of developing breast cancer)," said Dr. Christiane K. Kuhl of University Hospital Aachen, in Aachen, Germany.

"Women with dense breasts are at increased risk of being diagnosed with late-stage disease and with interval cancers - and it is interval-cancer rates that drive breast-cancer mortality of women who participate in screening. With abbreviated breast MRI (AB-MRI), we have an effective protection against this for women with dense breasts."

AB-MRI aims to reduce the complexity and cost of MRI and, thereby, improve access to breast MRI. Multiple studies have demonstrated equivalent diagnostic accuracy of AB-MRI with full MRI protocols.

Dr. Kuhl and colleagues from 48 academic centers, community hospitals and private practices in the U.S. and Germany compared the diagnostic performance of AB-MRI and DBT for screening average-risk women with dense breasts. The primary endpoint was the rate of invasive-cancer detection at the participant level.

Among 1,510 eligible women, 1,444 received both DBT and AB-MRI. Most women (77%) had heterogeneously dense breasts, 15% had extremely dense breasts and 8% who had dense breasts on their most recent prior mammogram were found to have nondense breasts at the time of the study.

Among the 19 invasive cancers in 17 women, AB-MRI detected the cancer in all 17 women, whereas DBT detected it in only seven women, with AB-MRI detecting seven more cases per 1,000 women compared with DBT, the researchers report in JAMA.

The sensitivity of AB-MRI for invasive cancer or ductal carcinoma in situ (DCIS) was significantly higher than that of DBT (95.7% vs. 39.1%, respectively). But specificity was significantly lower for AB-MRI than for DBT (86.7% vs. 97.4%).

Callback rates were 10.1% for screening DBT and 0% for AB-MRI, and additional imaging (either callback or short-term follow-up) was required in 7.5% for AB-MRI and 10.1% for DBT.

There were no interval cancers in the 1,407 women with complete follow-up information.

"If you have a woman with dense breast, AB-MRI for breast-cancer screening is a screening that will work," Dr. Kuhl said.

"Critics argue that AB-MRI, because it finds many more cancers, increases overdiagnosis, and that this could constitute more harm than good," she said. "As a matter of fact, and in particular in women with dense breasts, overdiagnosis is not our main problem. Rather, it is underdiagnosis: failure to find prognostically relevant cancers early enough."

"We have a huge unmet clinical need in women with dense breasts," Dr. Kuhl said. "They die of late undiagnosed breast cancer more than of any other cancer, and, for women under 50, more than of any other disease. I find it somewhat cynical to discredit an imaging method that can provide effective protection against such late diagnosis of cancer and just claim it may contribute to overdiagnosis."

Dr. Anna N. A. Tosteson of Geisel School of Medicine, Dartmouth College, in Lebanon, New Hampshire, who wrote a linked editorial, told Reuters Health by email, "Each woman should speak with her primary-care clinician about the breast-cancer screening approach that is most suitable for her among the options that are available to her. There is a range of breast densities and risks among women with dense breasts, so there is no single 'one size fits all' recommendation at this time."

"Women need tailored guidance on breast cancer screening, and the screening approach recommended should depend on the modalities available as well as her individual preferences," she said.

"It is very exciting to see the further development and study of innovative breast-cancer-screening approaches," Dr. Tosteson said. "Both the importance and challenges of fully evaluating the long-term outcomes associated with alternative approaches to screening should not be understated. They are real and yet women and their providers need to make breast-cancer-screening decisions with the information and options available today."

SOURCE: https://bit.ly/2PqCBZ7 and https://bit.ly/384quHT JAMA, February 25, 2020.

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