Second-look digital breast tomosynthesis (SL-DBT) in assessing incidental findings (IFs) at contrast-enhanced magnetic resonance imaging (CE-MRI) in patients with newly diagnosed breast cancer

Purpose: To test if SL-DBT, i.e. the re-evaluation of DBT images after CEMRI, helps assessing IFs at CE-MRI in patients with newly diagnosed breast cancer. Methods and Materials: Two experienced readers in consensus retrospectively reviewed the examinations of 43 patients who underwent DBT and CE-MRI from May 2012 to January 2013, looking for a DBT correlate of IFs at CE-MR. Standard of reference was histology for CE-MRI suspicious findings (ACR-BIRADS-3-5) and imaging follow-up for CE-MRI non-suspicious findings (ACR-BIRADS-1-2). Fisher exact test was used. Results: A total of 32 CE-MRI IFs were detected in 24 patients: 18 BIRADS-2 and 14 BIRADS-3-5. A DBT correlate was found in 12/24 IFs (38%) overall, 8/14 (57%) MR-BIRADS-3-5 and 4/18 (22%) MR-BIRADS-2 IFs, with borderline significance (p=0.080). Malignancy was histologically confirmed for 10/14 CE-MRI IFs; 6 of these 10 additional malignancies (60%) had a DBT correlate with suspicious features: 3 invasive lobular; 2 ductal carcinoma in situ; and 1 invasive ductal. A significantly lower rate of DBT correlate (6/22, 27%), was found for non-suspicious CE-MRI IFs, all with benign features (p=0.005). Conclusion: A DBT correlate was more frequent for malignant than for benign CE-MRI IFs. SL-DBT has the potential to confirm more than 50% of suspicious CE-MR IFs. However, the absence of a DBT correlate does not warrant to avoid MR-guided biopsy.