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Tuesday, December 03, 2013

Tomosynthesis Superior to Mammography in Breast Cancer Detection

Pragya A. Dang, M.D.

Tomosynthesis is significantly better than conventional mammography at detecting breast cancers and characterizing morphology, according to a session presented Monday.

There have been just a few clinical studies that have talked about the advantages of tomosynthesis over conventional mammography," said presenter Pragya A. Dang, M.D., of Massachusetts General Hospital, Boston. These include findings that the use of tomosynthesis reduces recall rates, improves diagnostic accuracy, and increases cancer detection.

"We wanted to delve further into our own experience and use the data we've collected over the last couple of years since we've been using tomosynthesis in clinical practice in order to access the maximum performance of these two technologies," Dr. Dang said.

Dr. Dang and colleagues retrospectively reviewed 172 biopsy-proven invasive breast cancers (142 invasive ductal carcinoma [IDC], 25 invasive lobular carcinoma [ILC] and 5 invasive mammary carcinoma) that were consecutively accrued prior to biopsy between March 2011 and October 2012. The cancers were imaged with tomosynthesis and conventional digital mammography.

Two radiologists rated the visibility and morphology of these cancers with both tomosynthesis and conventional mammography, and without the presence of prior imaging. "There was a significantly improved degree of visibility with tomosynthesis compared to digital mammography," Dr. Dang said.

As an example she highlighted a finding in which the readers, when asked to determine whether tomosynthesis performed better, the same, or worse than mammography, rated tomosynthesis as superior to mammography in visualizing cancers in 70 percent of the cases.

Lesion visibility was rated on a five-point scale, from 1 (not visible) to 5 (obvious). Visibility scores for IDC were 3.4 for tomosynthesis and 2.8 for mammography; for ILC scores were 3.2 for tomosynthesis and 2.3 for mammography. "So for both of these readers there was basically a one point improvement with tomosynthesis on the visibility score," Dr. Dang said. "And that is statistically significant."

Of the 172 cancers, 28 (16 percent) were occult on mammography, whereas just 5 (3 percent) were occult on tomosynthesis. Characterization of tumor morphology also improved with tomosynthesis, Dr. Dang said.

"Along with the improved visibility a much higher percentage of the cancers were more definitively characterized as masses compared to asymmetries, which were only available on one view," she said.

For example, she pointed out that the first reader was only able to characterize 42 percent of cancers as masses with conventional mammography, compared to 78 percent with tomosynthesis. Results were similar with the second reader, who was able to characterize 84 percent of the cancers as masses with tomosynthesis, compared to 36 percent with conventional mammography. But readers characterized 19 percent of the cancers as asymmetries on conventional mammography, compared to just 2 percent with tomosynthesis.

"So this better characterization of tumor morphology does help translate into improved detection of cancers," she said.

"Results show that tomosynthesis is significantly better than conventional mammography in visualizing cancers that we believe would translate to increased cancer detectability upon screening," she said. "It also provides more accurate morphology of cancers that allow for a better assessment of a lesion in initial imaging."

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© 2013 RSNA. The RSNA 2013 Daily Bulletin is the official publication of the 99th Scientific Assembly and Annual Meeting of the Radiological Society of North America. Published Sunday, December 1 - Thursday, December 5.

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