Racial differences in background parenchymal enhancement, a novel marker of breast cancer.

10528 Background: Breast density is a risk factor for breast cancer that can guide eligibility for supplemental screening including MRI, but Black women are less likely to qualify for supplemental screening due to having less dense breasts on average despite higher rates of breast cancer mortality. Background parenchymal enhancement (BPE), the enhancement of fibroglandular breast tissue on contrast-enhanced MRI, is a novel biomarker that has been shown to be a superior breast cancer risk marker than breast density. Women with high BPE levels have up to a four-fold increased risk of breast cancer, even after adjusting for density, but no studies have examined BPE exclusively among Black women. Methods: We identified Black and white women ages 40-74 with no prior history of breast cancer who had a mammogram and subsequent MRI as part of a screening or diagnostic work-up from 2016-2022 at our institution. BPE was qualitatively defined according to BI-RADS (Breast Imaging Reporting and Data System), with four ordinal levels of increasing enhancement: minimal, mild, moderate, and marked. We conducted a cross-sectional study to perform a logistic regression with race as the exposure and moderate or marked BPE as the outcome, using minimal and mild BPE as the reference group, adjusted for age and BI-RADS density. Results: We included 1027 Black women and 4834 white women in our analysis. Fewer Black women had extremely dense breasts compared to white women (6% vs 13%, p= 0.04), however, there was a larger proportion of high BPE (moderate or marked) in Black women compared to white women (32% vs 28%, p = 0.03) (Table). There was an inverse association between age and BPE levels (p = 0.03), and a positive association between density and BPE levels regardless of race (p< 0.01) (not shown). Black women were 39% more likely to have high BPE levels (95% CI: 1.39 1.19, 1.63), adjusted for age and density. Conclusions: Black women have lower density but higher BPE than white women, suggesting that BPE may improve identification of breast cancer risk for Black women. Participants Table: see text