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1809. The Clinical Significance of Background Parenchymal Enhancement (BPE) in High-Risk Women Compared with Average-Risk Population
Authors * Denotes Presenting Author
  1. Wakana Murakami *; University of California, Los Angeles
  2. Shabnam Mortazavi; University of California, Los Angeles
  3. Tiffany Yu; University of California, Los Angeles
  4. Nikhita Kathuria-Prakash; University of California, Los Angeles
  5. Stephanie Lee-Felker; University of California, Los Angeles
  6. Kelly McCann; University of California, Los Angeles
  7. Kyung Sung; University of California, Los Angeles
Objective:
To identify imaging features that predict a higher risk for breast cancer by comparing background parenchymal enhancement (BPE) between high-risk women and average-risk women.

Materials and Methods:
In this IRB-approved, HIPAA-compliant, retrospective study, we reviewed 1,872 consecutive patients who underwent breast MRI screening from January 2019 through December 2019 at a single academic institution (a total of 2,239 breast MRI scans). We identified women at different types of breast cancer risk associated with germline mutations and Tyrer-Cuzick model, and grouped them into four cohorts: 1) women with BRCA 1/2 germline mutations, 2) women with non-BRCA germline mutation, 3) women with 20% or more lifetime risk using Tyrer-Cuzick model, and 4) women at average risk for breast cancer (no germline mutation, no personal history of high-risk lesions and less than 20% lifetime risk). Exclusion criteria included: male, 1.5T MRI, incomplete MRI, without contrast study, non-screening indication, prior anti-estrogen therapy, and personal history of mastectomy, including prophylactic surgery. Clinical data such as age, lifetime risk, menopausal status, germline genetic predisposition, and hormonal therapy were collected. BPE was evaluated in accordance with BI-RADS (1-minimal, 2-mild, 3-moderate, and 4-marked). The Kruskal-Wallis test for three or more groups and Wilcoxon signed-rank test for two groups were used to compare BPE.

Results:
Four cohorts [138 MRIs (135 patients), 48 MRIs (45patients), 221 MRIs (219 patients), and 44 MRIs (44patients)] with the indication of screening for BRCA mutation carriers (Group 1), non-BRCA mutation carriers (Group 2), women with lifetime risk of 20% or more (Group 3), and average-risk population (Group 4) were identified, respectively. There were not significant differences between Group 1, 2, 3, and 4 (p=0.53). On the other hand, there were significant differences between Group 1 and Group 4 (p<0.001), Group 2 and Group 3 (p<0.001), Group 3 and Group 4 (p<0.001), pre-menopausal women without hormonal therapy in Group 1 and those in Group 3 (p<0.001), post-menopausal women without hormonal therapy in Group 1 and those in Group 3 (p<0.001), post-menopausal women without hormonal therapy in Group 2 and those in Group 3 (p<0.001).

Conclusion:
Our study demonstrated the significant differences of BPE evaluation between different types of breast cancer risk groups. Among high-risk patients, those with higher levels of BPE have been shown to have 2.1-2.5 times the risk of developing breast cancer compared to those with low BPE levels [1,2]. The differences are possibly influenced by the molecular and vascular environment related to genetic alteration of hormonal status [3]. When high BPE is observed in BRCA mutation carriers, these women are likely at higher risk for breast cancer and may benefit from chemoprevention.