RSNA: Dense breast tissue presents supplemental screening question

CHICAGO—When it comes to supplemental breast imaging for women with dense breasts but who are considered low risk, tomosynthesis could be a supplemental screening modality, while MRI screenings alongside digital mammography should be used for women at higher risk, according to a Nov. 30 presentation at the annual meeting of the Radiological Society of North America (RSNA).

“One of the reasons we’re talking about supplemental screening is that mammography is not perfect, and we all know that in the best of circumstances the sensitivity is around 85 percent, and sensitivity in mammography is lower in women who have dense breasts,” said Carol H. Lee, MD, of Memorial Sloan Kettering Cancer Center. “It can reach as low as 55 percent.”

Lee said high breast density has been shown to be an independent risk factor and in some cases the cancer risk for women with extremely dense breasts can be four to five times higher than women with mostly fatty tissue in their breasts. According Breast Cancer Screening Consortium data she provided, it’s estimated that 43 percent of women have heterogeneously or extremely dense breasts. This translates to more than 27 million women in the U.S. aged 40 to 74 with dense breasts.

“Do we screen all of them? Some of them? None of them?” asked Lee.

When it comes to supplemental screening of women with dense breasts. Lee said tomosynthesis is a growing trend that could benefit patients in cancer detection, though its use as supplemental imaging is still new. But to Lee, its potential is promising.

“The most striking benefit of tomosynthesis has been a decreased recall rate,” she said. “It’s basically a mammography technique that relies on density difference between cancer and the immediate surrounding tissue.”

Additionally, Lee said a number of recent screening studies have shown incremental cancer detection rates with ultrasound over mammography, about three or four additional cancers detected per 1,000 screenings.

“The cancers that it picks up tend to be small, they tend to be invasive and high percentage of them are node negative, which is all very good,” Lee said of ultrasound.

Drawbacks to ultrasound as a supplemental imaging modality include being operator dependent, a high rate of BIRADS 3 lesions, and in average risk women the yield is relatively low when it comes to cancer detection. “[W]hen you look at the number of false positives with ultrasound, cost becomes an issue, too,” Lee said.

For the most sensitive supplemental screening test, Lee said MRI is the answer. “When you add MRI to mammography, you increase the cancer detection to 56 percent as opposed to 24 percent by adding ultrasound."

Lee suggested the future of screening for all women might find tomosynthesis replacing digital mammography, but it's unclear whether that will be sufficient to reduce missed cancers. For asymptomatic women with no additional risk factor other than having dense breasts, Lee suggested ultrasound for the supplemental screening.

“And for women with intermediate and high risk women, I think it’s been shown that MRI is the best supplemental screening tool to use,” Lee said.