Background parenchymal enhancement on breast MRI: A comprehensive review

Abstract

The degree of normal fibroglandular tissue that enhances on breast MRI, known as background parenchymal enhancement (BPE), was initially described as an incidental finding that could affect interpretation performance. While BPE is now established to be a physiologic phenomenon that is affected by both endogenous and exogenous hormone levels, evidence supporting the notion that BPE frequently masks breast cancers is limited. However, compelling data have emerged to suggest BPE is an independent marker of breast cancer risk and breast cancer treatment outcomes. Specifically, multiple studies have shown that elevated BPE levels, measured qualitatively or quantitatively, are associated with a greater risk of developing breast cancer. Evidence also suggests that BPE could be a predictor of neoadjuvant breast cancer treatment response and overall breast cancer treatment outcomes. These discoveries come at a time when breast cancer screening and treatment have moved toward an increased emphasis on targeted and individualized approaches, of which the identification of imaging features that can predict cancer diagnosis and treatment response is an increasingly recognized component. Historically, researchers have primarily studied quantitative tumor imaging features in pursuit of clinically useful biomarkers. However, the need to segment less well-defined areas of normal tissue for quantitative BPE measurements presents its own unique challenges. Furthermore, there is no consensus on the optimal timing on dynamic contrastenhanced MRI for BPE quantitation. This article comprehensively reviews BPE with a particular focus on its potential to increase precision approaches to breast cancer risk assessment, diagnosis, and treatment. It also describes areas of needed future research, such as the applicability of BPE to women at average risk, the biological underpinnings of BPE, and the standardization of BPE characterization. Level of Evidence: 3 Technical Efficacy Stage: 5

Contralateral parenchymal enhancement on breast MRI before and during neoadjuvant endocrine therapy in relation to the preoperative endocrine prognostic index

“…Our results are in agreement with the findings of Hilal et al, who found that high pretreatment BPE, classified according to the BI-RADS lexicon, was associated with non-responders after NET [ 13 ]. In the NAC setting, BPE has been linked to several treatment outcomes [ 6 ]: a high BPE before start of NAC was associated with worse recurrence-free survival (RFS) [ 30 ], while a decrease in BPE during NAC was associated with pCR [ 31 – 33 ].…”

<p>Predictors of Neoadjuvant Chemotherapy Response in Breast Cancer: A Review</p>

“…However, BPE is influenced by endogenous and exogenous hormone levels, so its application in breast cancers may be somehow limited. 115 Therefore, researches tried to find that PET/CT imaging features might be potential predictors of pCR rate of NAC in locally advanced breast cancer patients, 116 but the cost and inconvenience hindered its way to be used broadly. Simultaneously, an increasing number of scientists are endeavoring to find the breaking points in cancerous treatments by investigating the tumor microenvironments, such as surrounding immune cells, adipocytes, secreted small molecules and so on.…”

Current Landscape of Breast Cancer Imaging and Potential Quantitative Imaging Markers of Response in ER-Positive Breast Cancers Treated with Neoadjuvant Therapy

“…Quantitative approaches based on percent enhancement (PE) within the region or volume of interest in 2D or 3D have also been used to describe BPE. A recent review of BPE on breast MRI by Liao et al has summarized the variation of imaging protocol and the different approaches of BPE quantification [100]. Without the consensus of optimal timing for measurements and no standardization of BPE calculations, it is difficult to implement quantitative BPE to clinical practice.…”

“…Since the initial report linking BPE to the risk of breast cancer diagnosis [101], many subsequent studies have demonstrated that treatment-induced changes of BPE in the ipsilateral or contralateral breast may also serve as a predictor of tumor response [100]. In the NAC setting, post-treatment reduction of BPE from baseline was associated with tumor response or pCR [102][103][104][105].…”