| Summary: | 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 fixedeffect
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.
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