Background Parenchymal Enhancement on Breast MRI as a Prognostic Surrogate: Correlation With ‎Breast Cancer Oncotype Dx Score

Abstract

Purpose: Breast MRI background parenchymal enhancement (BPE) can potentially serve as a prognostic marker, ‎by possible correlation with molecular subtype. Oncotype Dx, a gene assay, is a prognostic and ‎predictive surrogate for tumor aggressiveness and treatment response. The purpose of this study was ‎to investigate the association between contralateral non-tumor breast magnetic resonance imaging ‎‎(MRI) background parenchymal enhancement and tumor oncotype score.‎

Methods: In this retrospective study, patients with ER+ and HER2− early stage invasive ductal carcinoma who ‎underwent preoperative breast MRI, oncotype risk scoring, and breast conservation surgery from ‎‎2008–2010 were identified. After registration, BPE from the pre and three post-contrast phases was ‎automatically extracted using a k-means clustering algorithm. Four metrics were calculated: initial ‎enhancement (IE) relative to the pre-contrast signal, late enhancement, overall enhancement (OE), ‎and area under the enhancement curve (AUC). Histogram analysis was performed to determine first ‎order metrics which were compared to oncotype risk score groups using Mann–Whitney tests and ‎Spearman rank correlation analysis.‎

Results: This study included 80 women (mean age = 51.1 ± 10.3 years); 46 women were categorized as low risk ‎‎(≤17) and 34 women were categorized as intermediate/high risk (≥18) according to Oncotype Dx. For ‎the mean of the top 10% pixels, significant differences were noted for IE (p = 0.032), OE (p = 0.049), ‎and AUC (p = 0.044). Using the risk score as a continuous variable, correlation analysis revealed a weak ‎but significant correlation with the mean of the top 10% pixels for IE (r = 0.26, p = 0.02), OE (r = 0.25, p = ‎‎0.02), and AUC (r = 0.27, p = 0.02).‎

Conclusion: BPE metrics of enhancement in the non-tumor breast are associated with tumor Oncotype Dx ‎recurrence score, suggesting that the breast microenvironment may relate to likelihood of recurrence ‎and magnitude of chemotherapy benefit.‎