Abstract
Breast density, a measure of dense fibroglandular tissue relative to non-dense fatty tissue, is confirmed as an independent risk factor of breast cancer. Although there has been an increasing interest in the quantitative assessment of breast density, no research has investigated the optimal technical approach of breast MRI in this aspect. Therefore, we performed a systematic review and meta-analysis to analyze the current studies on quantitative assessment of breast density using MRI and to determine the most appropriate technical/operational protocol. Databases (PubMed, EMBASE, ScienceDirect, and Web of Science) were searched systematically for eligible studies. Single arm meta-analysis was conducted to determine quantitative values of MRI in breast density assessments. Combined means with their 95% confidence interval (CI) were calculated using a fixed-effect model. In addition, subgroup meta-analyses were performed with stratification by breast density segmentation/measurement method. Furthermore, alternative groupings based on statistical similarities were identified via a cluster analysis employing study means and standard deviations in a Nearest Neighbor/Single Linkage. A total of 38 studies matched the inclusion criteria for this systematic review. Twenty-one of these studies were judged to be eligible for meta-analysis. The results indicated, generally, high levels of heterogeneity between study means within groups and high levels of heterogeneity between study variances within groups. The studies in two main clusters identified by the cluster analysis were also subjected to meta-analyses. The review confirmed high levels of heterogeneity within the breast density studies, considered to be due mainly to the applications of MR breast-imaging protocols and the use of breast density segmentation/measurement methods. Further research should be performed to determine the most appropriate protocol and method for quantifying breast density using MRI.
Highlights
Breast density, a measure of dense fibroglandular tissue relative to non-dense fatty tissue, is an independent risk factor for breast cancer [1,2,3]
The evaluation of breast density based on mammograms is limited due to the overlapping of tissues, variations in breast compression, and inappropriate positioning that lead to artefacts and inclusion of insufficient breast tissue [6,7]
Breast density is assessed qualitatively using the American College of Radiology (ACR) Breast Imaging-Reporting and Data System (BI-RADS) atlas, which is a classification system commonly used for mammography, according to which density has four categories based on the amount of fibroglandular tissue: “(1) almost entirely fat, (2) scattered fibroglandular tissue, (3) heterogeneous fibroglandular dense and (4) extreme fibroglandular tissue” [14,15]
Summary
A measure of dense fibroglandular tissue relative to non-dense fatty tissue, is an independent risk factor for breast cancer [1,2,3]. Breast density is assessed qualitatively using the American College of Radiology (ACR) Breast Imaging-Reporting and Data System (BI-RADS) atlas, which is a classification system commonly used for mammography, according to which density has four categories based on the amount of fibroglandular tissue: “(1) almost entirely fat, (2) scattered fibroglandular tissue, (3) heterogeneous fibroglandular dense and (4) extreme fibroglandular tissue” [14,15]. The interpretations of these four categories are applied for MRI. Each of these methods were shown to have advantages and limitations through the use of semi-automatic thresholding and segmentation approaches for quantitative assessment of breast density
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