Screening Breast MR Imaging: Comparison of Interpretation of Baseline and Annual Follow-up Studies

To determine whether baseline screening breast magnetic resonance (MR) imaging studies have a higher rate of follow-up or biopsy recommendation than do studies with prior MR images available for comparison. This was an institutional review board-approved, HIPAA-compliant, retrospective study. Informed consent was waived. Reports from 650 consecutive screening breast MR imaging examinations performed in women between September 2007 and December 2008 were reviewed. All examinations were performed by using the same protocol, and images were interpreted by the same radiologists. Presence of comparison studies, Breast Imaging Reporting and Data System (BI-RADS) category, and biopsy results were recorded. Data were analyzed by using the χ(2) test, the two-sample test of proportions, and the Fisher exact test. Mean patient age was 51 years (range, 25-81 years). Of the baseline studies, findings in 31 of 307 (10.1%) were interpreted as BI-RADS category 3 and findings in 18 of 307 (5.9%) were interpreted as BI-RADS category 4 or 5. Of the examinations with findings classified as BI-RADS category 4 or 5, the results in two of 18 (11.1%) were positive for malignancy at biopsy. Of the examinations with prior MR images for comparison, findings in nine of 343 (2.6%) were interpreted as BI-RADS category 3 and findings in 16 of 343 (4.7%) were interpreted as BI-RADS category 4 or 5. Of the examinations with findings classified as BI-RADS category 4 or 5, the results in three of 16 (18.8%) were positive for malignancy at biopsy. The difference in the number of BI-RADS category 3 interpretations between the two groups was significant (P < .001), but there was no significant difference in BI-RADS category 4 or 5 interpretations or positive predictive values. Baseline screening MR imaging was associated with a higher likelihood of recommendation for short-interval follow-up than was MR imaging with prior images for comparison.