Background parenchymal enhancement on breast MRI: association with recurrence-free survival in patients with newly diagnosed invasive breast cancer.

PURPOSE: To determine whether BPE in preoperative breast MRI influences patients' recurrence-free survival (RFS).
METHODS: Between February 2010 and December 2011, 804 consecutive women with invasive breast cancer who had undergone preoperative breast MRI and curative cancer surgery were identified. BPE was visually graded by two reviewers. We determined the correlation between BPE grade and other clinicopathological variables, including age, adjuvant therapy, menopausal status, histologic grade, T stage, N stage, lymphovascular invasion, molecular subtype, surgical margin status, and mammographic density. A Cox proportional hazards model was used to analyze the effects of clinicopathological variables and radiological findings (BPE grade, mammographic density) on RFS.
RESULTS: High BPE was associated with premenopausal status (Ps < 0.0001), higher mammographic density (Ps < 0.0001), progesterone receptor positivity (Ps = 0.039, 0.007, respectively), presence of lymphovascular invasion (Ps = 0.008, 0.001, respectively), and close surgical margin (Ps < 0.0001). Recurrences were observed in 75 patients after a mean follow-up period of 61.8 months (range 4-81 months). Non-minimal BPE grade (RFS hazard ratio = 3.086, P = 0.003 for reader 1; RFS hazard ratio = 2.221, P = 0.075 for reader 2) and T3 stage were associated with worse outcomes in postmenopausal women. In premenopausal women, non-minimal BPE grade by readers 1 and 2 did not affect the patients' outcomes.
CONCLUSIONS: Increased BPE on preoperative breast MRI in postmenopausal women has potential as a predictor of poor RFS.