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J Clin Oncol. 2019 Jan 9:JCO1800378. doi: 10.1200/JCO.18.00378. [Epub ahead of print]

Population-Based Assessment of the Association Between Magnetic Resonance Imaging Background Parenchymal Enhancement and Future Primary Breast Cancer Risk.

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1 Kaiser Permanente Medical Center, Vallejo, CA.
2 University of California, San Francisco, San Francisco, CA.
3 University of California, Davis, Davis, CA.
4 Kaiser Permanente Washington Health Research Institute, Kaiser Permanente Washington, Seattle, WA.
5 University of Vermont Cancer Center, University of Vermont, Burlington, VT.
6 Advocate Lutheran General Hospital, Park Ridge, IL.
7 University of North Carolina, Chapel Hill, NC.
8 University of Washington, and Seattle Cancer Care Alliance, Seattle, WA.
9 Norris Cotton Cancer Center and Geisel School of Medicine at Dartmouth, Lebanon, NH.
10 Institute for Health Research and Policy, University of Illinois at Chicago, Chicago, IL.
11 Massachusetts General Hospital, Harvard Medical School, Boston, MA.



To evaluate comparative associations of breast magnetic resonance imaging (MRI) background parenchymal enhancement (BPE) and mammographic breast density with subsequent breast cancer risk.


We examined women undergoing breast MRI in the Breast Cancer Surveillance Consortium from 2005 to 2015 (with one exam in 2000) using qualitative BPE assessments of minimal, mild, moderate, or marked. Breast density was assessed on mammography performed within 5 years of MRI. Among women diagnosed with breast cancer, the first BPE assessment was included if it was more than 3 months before their first diagnosis. Breast cancer risk associated with BPE was estimated using Cox proportional hazards regression.


Among 4,247 women, 176 developed breast cancer (invasive, n = 129; ductal carcinoma in situ,n = 47) over a median follow-up time of 2.8 years. More women with cancer had mild, moderate, or marked BPE than women without cancer (80% v 66%, respectively). Compared with minimal BPE, increasing BPE levels were associated with significantly increased cancer risk (mild: hazard ratio [HR], 1.80; 95% CI, 1.12 to 2.87; moderate: HR, 2.42; 95% CI, 1.51 to 3.86; and marked: HR, 3.41; 95% CI, 2.05 to 5.66). Compared with women with minimal BPE and almost entirely fatty or scattered fibroglandular breast density, women with mild, moderate, or marked BPE demonstrated elevated cancer risk if they had almost entirely fatty or scattered fibroglandular breast density (HR, 2.30; 95% CI, 1.19 to 4.46) or heterogeneous or extremely dense breasts (HR, 2.61; 95% CI, 1.44 to 4.72), with no significant interaction ( P = .82). Combined mild, moderate, and marked BPE demonstrated significantly increased risk of invasive cancer (HR, 2.73; 95% CI, 1.66 to 4.49) but not ductal carcinoma in situ (HR, 1.48; 95% CI, 0.72 to 3.05).


BPE is associated with future invasive breast cancer risk independent of breast density. BPE should be considered for risk prediction models for women undergoing breast MRI.


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