Session 2: Background Parenchymal Enhancement on Surveillance Breast MRI in Women with a Personal History of Primary Breast Cancer: Association with Future Second Breast Cancer Risk

Purpose: To investigate whether the background parenchymal enhancement (BPE) on surveillance breast MRI is associated with subsequent second breast cancer risk in women with a personal history of primary breast cancer.

Materials and Methods: A retrospective search of our imaging database identified consecutive breast MRI examinations performed between January 2008 and December 2017 in women who had undergone surgical treatment for primary breast cancer and had no history of locoregional recurrence. BPE on breast MRI was qualitatively assessed using a four-category classification of minimal, mild, moderate, or marked. Data on women’s age at the time of initial breast cancer diagnosis, family history of breast cancer in first-degree relatives, BRCA genetic test results, histopathologic characteristics of primary breast cancer, time interval between the initial breast cancer surgery and the breast MRI examination, and mammographic breast density within one year of breast MRI were collected. Future second breast cancer was defined as ipsilateral or contralateral breast cancer diagnosed at least 6 months after an MRI examination. Factors associated with second breast cancer risk were estimated using the Cox proportional hazards regression.

Results: Of 2734 women (mean age, 47 years ± 8 [standard deviation]), 114 developed a second breast cancer (ipsilateral, n = 54; contralateral, n = 58; ipsilateral and contralateral, n = 2) at a median follow-up of 5.6 years (range, 0.5-12.9 years). In multivariable analysis, younger age ( < 45 years) at initial breast cancer diagnosis (hazard ratio [HR], 1.7; 95% CI: 1.2, 2.4; P = .01), presence of BRCA gene mutation (HR, 3.7; 95% CI: 2.0, 6.7; P <.001), negative hormone receptor expression in the initial breast cancer (HR, 1.8; 95% CI: 1.2, 2.8; P = .01), and mild, moderate, or marked BPE on surveillance breast MRI (HR, 1.8; 95% CI: 1.3, 2.6; P = .001) were significantly associated with second breast cancer risk. Mild, moderate, or marked BPE demonstrated significantly increased risk of second breast cancer in women with dense breasts (HR, 2.0; 95% CI: 1.3, 2.9; P < .001) and breast MRI performed 2 years after initial breast cancer surgery (HR, 3.9; 95% CI: 1.7, 9.1; P = .002).

Conclusion: BPE on surveillance breast MRI is an independent predictor of second breast cancer risk in women with a personal history of primary breast cancer.

Clinical Relevance Statement: BPE on surveillance breast MRI can be used to stratify the risk of developing second breast cancer in women with a personal history of primary breast cancer.