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Monday, December 02, 2013

Digital Breast Tomosynthesis Offers Superior Pre-surgical Staging

Asif Iqbal, M.D.

Digital breast tomosynthesis has the potential to replace full-field digital mammography (FFDM) for assessing invasive breast cancer, according to a digital presentation on display in the Lakeside Learning Center this week. The research earned a 2013 RSNA Trainee Research Prize awarded Sunday.

Although FFDM and ultrasound are the proven imaging modalities for detecting breast cancer, presenter Asif Iqbal, M.D., said digital breast tomosynthesis is an emerging technology which is showing better accuracy in measuring the tumor sizes.

Two main problems are associated with FFDM, according to Dr. Iqbal, of the Breast Radiology Department of the National Breast Screening Centre at King's College Hospital in London, and colleagues. Anatomical noise from breast parenchyma can obscure tumors, and certain growth patterns, such as diffusely infiltrating invasive lobular carcinoma, have relatively little fibrous or connective tissue growth around the tumor. "The characterization of the lesion—the extent of the tumor margins and the boundary of the lesion—are not as easily visible on FFDM," Dr. Iqbal said.

Digital breast tomosynthesis overcame these problems. "In particular, on the spiculated masses, which appear as a star shape, the spicules coming out from the nucleus of the tumor are easily visible, but they aren't as easily visible on FFDM," Dr. Iqbal said.

Researchers also found that digital breast tomosynthesis had a tendency to "over-measure" the size of tumors, whereas ultrasound had a tendency to "under-measure." The team also reported changes in mammographic signs between the two modalities.

"Comparing FFDM with tomosynthesis, sometimes you would find that a lesion with asymmetric density or parenchymal distortion would change into a spiculated mass on digital breast tomosynthesis," Dr. Iqbal said. "Mammographic sign change is one of the most significant benefits."

"Because of the glandular appearance of the tissue on the 2D, especially in dense breasts, it may not be easy to find the foci of the tumor and the reader may classify it as normal, or BI-RADS 1," Dr. Iqbal said. "But on the FFDM, because of the 3D information within the slices, sometimes we have noticed that it changes into a circumscribed or a spiculated mass."

Researchers studied 139 breast lesions in 137 patients, who averaged 58 years. The team found that 77.7 percent of the cancers were invasive ductal carcinoma, 15.8 percent were invasive lobular carcinoma, 2.2 percent were mucinous carcinoma, and 2.8 percent were tubular carcinoma. There was one case each of medullary, lymphovascular and papillary carcinoma. Of the three tested modalities—FFDM, digital breast tomosynthesis and ultrasound—tomosynthesis offered the highest degree of accuracy in determining maximum tumor dimension, with a greater ability to determine tumor margins.

Dr. Iqbal said he believes that digital breast tomosynthesis has the potential to provide the best tumor staging for preoperative management. "It will help in accurate tumor size measurement, which will in turn be important especially in conservative breast surgery. It will help us choose the surgical option that is best for the patient."

The superior measurement of digital breast tomosynthesis compared to FFDM and ultrasound is mainly due to the additional information in the three-dimensional series of thin slices, which allows better lesion visibility and better measurement of lesion extent and characteristics, the researchers noted.

Dr. Iqbal and his team are further exploring the use of "synthetic 2D" generated with tomosynthesis. "I foresee that synthetic 2D combined with the 3D slices of the tomosynthesis could replace the existing conventional 2D mammography," Dr. Iqbal said.

Dr. Iqbal's research earned a 2013 RSNA Trainee Research Prize honoring an outstanding scientific presentation in each subspecialty presented by a resident/physics trainee, fellow or medical student.

The scientific poster, LL-BRS-SU1A, Measurement of Invasive Breast Cancer Using Digital Breast Tomosynthesis, Full Field Digital Mammography and Ultrasonography, is on display in the Lakeside Learning Center this week. Virtual Meeting registrants can log in to view the poster from outside McCormick Place.

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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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