Background Parenchymal Enhancement Over Exam Time in Patients With and Without Breast Cancer

Purpose: To compare background parenchymal enhancement (BPE) over time in patients with and without breast cancer. Materials and Methods: This retrospective Institutional Review Board (IRB)-approved, Health Insurance Portability and Accountability Act (HIPAA)-compliant study included 116 women (25-84 years, mean 54 years) with breast cancer who underwent breast magnetic resonance imaging at 3T between 1/2/2009 and 12/29/2009 and 116 age and date-ofexam- matched women without breast cancer (23-84 years, mean 51 years). Two independent, blinded readers (R1, R2) recorded BPE (minimal, mild, moderate, marked) at three times (100, 210, and 320 seconds postcontrast). Subsequent cancers were diagnosed in 9/96 control patients with follow up (12.6-93.0 months, mean 63.6 months). Exact MannWhitney, Fisher's exact, and McNemar tests were performed. Results: Mean BPE was not found to be different between patients with and without breast cancer at any time (P=0.36-0.64). At time 2 as compared with time 1, there were significantly more patients, both with and without breast cancer, with BPE > minimal (R1: 90 vs. 41 [P < 0.001] and 81 vs. 36 [P < 0.001]; R2: 84 vs. 52 [P < 0.001] and 79 vs. 43 [P < 0.001]) and BPE > mild (R1: 59 vs. 10 [P < 0.001] and 47 vs. 13 [P < 0.001]; R2: 49 vs. 12 [P < 0.001] and 41 vs. 18 [P < 0.001]). BPE changes between times 2 and 3 were not significant (P=0.083-1.0). Odds ratios for control patients developing breast cancer were significant only for R2 and ranged up to 7.67 (1.49, 39.5; P < 0.01) for BPE > mild at time 2. Conclusion: BPE changes between the first and second postcontrast scans and stabilizes thereafter in most patients. Further investigation into the most clinically relevant timepoint for BPE assessment is warranted.