Breast MRI fibroglandular volume and parenchymal enhancement in BRCA1 and BRCA2 mutation carriers before and immediately after risk-reducing salpingo-oophorectomy

OBJECTIVE. The purpose of this article is to assess the difference in fibroglandular volume and background parenchymal enhancement in BRCA1 and BRCA2 mutation carriers on contrast-enhanced breast MRI (CE-MRI) performed before and immediately after risk-reducing salpingo-oophorectomy (RRSO). MATERIALS AND METHODS. We retrospectively compared fibroglandular volume and background parenchymal enhancement in 55 female BRCA1 and BRCA2 mutation carriers before and after RRSO using standard BI-RADS categories and a paired Wilcoxon and Mann-Whitney U test. A two-sample Wilcoxon test was performed to compare fibroglandular volume and background parenchymal enhancement in women with and without subsequent breast cancer diagnosis on follow-up. RESULTS. The median time to post-RRSO CE-MRI was 8 months (range, 1-40 months). There was no difference in fibroglandular volume before and after RRSO (p = 0.65). The mean background parenchymal enhancement was 2.5 (range, 1-4) before and 1.5 (range, 1-4) after RRSO (overall range, -2.5 to 1.5; p = 0.0001). Breast cancer was detected in nine women at a median time of 4.8 years (range, 1.8-13.3 years) after RRSO. For women who received a diagnosis of breast cancer after RRSO compared with those who did not, mean background parenchymal enhancement before RRSO was 3 (range, 2-4) versus 2.5 (range, 1-4; p = 0.001), and mean background parenchymal enhancement after RRSO was 2.5 (range, 1.5-4) versus 1.5 (range 2-4; p = 0.0018). There was no difference in fibroglandular volume before and after RRSO. CONCLUSION. In BRCA1 and BRCA2 mutation carriers, we observed a significant reduction in background parenchymal enhancement on the first CE-MRI after RRSO and no significant change in fibroglandular volume. Higher background parenchymal enhancement before and after RRSO was observed in women who subsequently received a diagnosis of breast cancer. This suggests that background parenchymal enhancement, rather than fibro-glandular volume, may be a more sensitive imaging biomarker of breast cancer risk.