Study Suggests Role of MR Imaging after DBT Should be Reassessed

By Elizabeth Gardner

Amy Chudgar, M.D.

Is it necessary to perform MR imaging after digital breast tomosynthesis (DBT) to detect additional disease in patients diagnosed with breast cancer? A study presented Monday suggests that preoperative use of MR imaging in breast cancer patients be reevaluated as DBT replaces 2D digital mammography.

Routine use of MR imaging to screen newly diagnosed breast cancer is already controversial and varies greatly from institution to institution, said presenter Amy Chudgar, M.D., of the Hospital of the University of Pennsylvania (HUP), who was awarded a Trainee Research Prize—Resident, for her research, "Digital Breast Tomosynthesis versus Digital Mammography Detected Cancers: Assessment of Disease Extent on MRI."

"Some surgeons do MRIs on every patient preoperatively, while others will do the exam at the patient's request," Dr. Chudgar said.

While some previous studies have shown that preoperative MR imaging detects more disease and is useful for planning surgeries, other studies have discovered a high rate of false positive results that can lead to unnecessary surgery. Some recent studies also show that DBT is superior to 2D digital mammography at discovering cancers, suggesting the DBT alone may be enough to detect the full extent of disease.

HUP began using DBT for all screenings in 2011. While the hospital's current protocols call for doing both DBT and 2D digital mammography on each patient, Dr. Chudgar says that the dual exam will be phased out as more data is accumulated on the effectiveness of DBT.

The retrospective study reviewed more than 24,000 DBT-screened patients and almost 11,000 DM-screened patients. Of the DBT patients, 235 had a subsequent MR imaging exam, and 83 of those were for staging newly diagnosed breast cancer. Of the DM patients, 83 patients had a subsequent MR imaging exam and 26 of those were for cancer staging. In the DBT cohort, MR imaging detected additional disease in 10 percent of patients. However, the MR imaging exam produced false positives for 14 percent of patients. For the remaining 76 percent, the MR imaging exam didn't add any new information. In the DM cohort, 30 percent of the MR imaging exams detected additional disease, while 13 percent were false positives and 57 percent didn't add any new information.

During her talk, Dr. Chudgar also briefly addressed the issue of breast density. She did the same analysis but further compared patients with dense breasts to those with non-dense breasts. The cohort with non-dense breasts had more true positives with DM than with DBT, and also had a higher rate of "no additional findings" with DBT, suggesting that DBT is an especially effective technique for detecting additional disease in non-dense breasts.

"MRI does detect additional cancer in both groups, but for patients whose cancer was detected with DBT, the MRI results had fewer true positives," Dr. Chudgar said. "We know there are limitations to the study, and it should be researched further because the population size is low and we don't have information for long-term follow-up. We'd also like to do further analysis on breast density."

RSNA 2014 Sessions Focus on Breast MR Imaging Research

Dr. Chudgar is part of other research teams presenting related research this week:

  • "Pictorial Review of Breast MRI Utilization in Two Screening Populations: Digital Mammography versus Digital Breast Tomosynthesis," Education Exhibit (BRE137) in the BR Community, Learning Center.
  • "Utilization of MRI as a Problem Solving Tool Prior to and Following the Implementation of Screening DBT," Scientific Paper (SSK01-05), 11:10-11:20 a.m., Wednesday, Dec. 3
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