Jennifer Xiao1, Michael Hirano1, Daniel Hippe1, Neal Shekar 1, Mara Rendi2, Kevin Cheung3, Habib Rahbar1, and Savannah Partridge 1
1Radiology, University of Washington, Seattle, WA, United States, 2Pathology, University of Washington, Seattle, WA, United States, 3Medicine, University of Washington, Seattle, WA, United States
Synopsis
Although kinetics are
routinely incorporated into interpretation of contrast enhanced breast MRI,
there is a paucity of literature supporting the association between the pathophysiologic
basis of enhancement and its histopathologic correlate. Our study investigated
DCE-MRI kinetic parameters and texture features analyzed with radiomics and
their correlation with microvessel density as a surrogate for tumor
angiogenesis. Twenty seven patients with invasive breast cancer were included
in our study. Both peak SER and washout fraction and several texture features
were significantly correlated with microvessel density (p<0.01), further supporting
the biologic basis of malignant enhancement on breast MRI.
Introduction
Both benign and
malignant breast lesions are known to enhance on dynamic contrast enhanced MRI
(DCE-MRI), with several kinetic features associated with malignancy (1-3). Although
we routinely incorporate kinetic parameters in our interpretation of DCE-MRI,
there is a paucity of literature supporting the association between the
pathophysiologic basis of enhancement on MRI and its histopathologic correlate.
DCE-MRI kinetic features are presumed to reflect tumor angiogenesis, a
necessary step in breast cancer growth and metastasis (4-5). Microvessel
density is a pathological marker used to quantify tumor angiogenesis and has
been shown to predict poor survival in women with invasive breast cancer (6). The
purpose of our study was to investigate whether DCE-MRI quantitative kinetic
parameters and texture features analyzed with radiomics correlate with MVD as a
surrogate for tumor angiogenesis. Methods
After IRB approval,
patients with newly diagnosed invasive breast cancer were consented prior to
preoperative breast MRI. Routine clinical evaluation of core biopsies included
histologic type, Nottingham grade, ER, PR, and HER2 expression and Ki-67.
Microvessel density (MVD) was also assessed by a pathologist after
immunostaining with CD31 and categorized as high (3+), intermediate (2+), and
low (1+). Imaging was performed on a 3 Tesla Philips Achieve TX scanner with a
16-channel breast MRI coil. Multiparametric breast MR examinations included:
T2-weighted, diffusion-weighted imaging (DWI), and dynamic contrast-enhanced
MRI performed with pre-contrast and post-contrast volumes center at 2,5, and 8
minutes after contrast injection (0.1mmol/kg-body weight gadoteridol delivered
at 2cc/sec with 15cc saline flush).
Contrast kinetics were
characterized using custom software as previously described (7), including: 1)
initial peak enhancement (PE) at 2mins post-contrast, 2) signal enhancement
ratio (SER) characterizing slope of the delayed enhancement curve, 3)
functional tumor volume (FTV) calculated by summing all voxels with PE ≥50%,
and 4) washout fraction (WF) calculated as the percentage of total tumor voxels
with SER ≥1.1, reflecting washout. Peak PE and peak SER were determined for
hot-spot regions of 3x3x3 voxels (0.1625 mm3) producing the highest
mean PE and SER value, respectively. For radiomics texture analysis, lesions were
segmented by thresholding initial post-contrast DCE images and evaluated using
an open source software platform (3D Slicer v4.11.0 with pyradiomics library,
www.slicer.org). Each DCE MR image was normalized to have zero mean and unity
standard deviation and isotropic resampling was applied before the radiomics
features were calculated for the ROI segmentation. A total of 108 features categorized as first
order, shape, and various texture features were generated for further
statistical analysis.
Associations between MVD category
and individual imaging features were summarized using the odds ratio (OR) from
univariable logistic regression models. ORs were scaled to correspond to change
per 1-SD increase in the feature. Differences between high and low MVD groups
were tested using the Wilcoxon rank-sum test and summarized using the area
under the receiver operating characteristic curve (AUC). P-values were not adjustment for multiple
testing so the radiomics texture analysis should be considered hypothesis-generating.Results
Our study included 27
patients (median age 53, range 30-88) with breast cancer (23 invasive ductal
carcinoma, 3 invasive lobular carcinoma, 1 invasive mammary carcinoma). Mean
tumor size was 29.7 mm with a range of 10 to 101 mm. Both peak SER and washout fraction
were positively associated with MVD. Lesions
with higher MVD exhibited higher peak SER values (mean: 1.8 vs. 1.5, AUC = 0.84,
p = 0.005) and
higher washout fraction (mean: 40% vs. 20%, AUC = 0.86, p = 0.003) than lesions with low MVD, Table 1.
Examples of two lesions with high and low MVD are shown in Figure 1. There was no significant correlation
between peak PE or FTV with MVD (p= 0.59 and 0.44, respectively). Several
radiomics texture features were also found to be associated with MVD, including
several GLDM features, GLCM features and GLRLM features (p<0.05). Two features
in particular, GLDM- LargeDependenceHighGrayLevelEmphasis
and GLRLM- LongRunHighGrayLevelEmphasis, were significantly
correlated with MVD (AUC = 0.82, p = 0.009 for each). Conclusion and Discussion
Our study supports
that quantitative tumor kinetic parameters and texture features on DCE-MRI allow
noninvasive characterization of tumor angiogenesis as measured by MVD in
patients with invasive breast cancer. These findings may aid in improving
biologic stratification of lesion aggressiveness and metastatic potential. Due
to the small sample size, further multivariate analysis was not possible for
this study and additional studies are warranted to investigate optimal DCE MRI
predictive models. Acknowledgements
Supported by Fred Hutchinson Cancer Center Support Grant P30 CA015704, NIH/NCI R01CA207290 (SCP), NIH/NCI R01CA203883 (HR), and Department of Defense W81XWH-18–1–0098 (KJC).
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