Jacob Antunes1, Scott Steele2, Conor Delaney2, Joseph Willis3, Justin Brady4, Rajmohan Paspulati5, Anant Madabhushi1, and Satish Viswanath1
1Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States, 2Department of Colon and Rectal Surgery, University Hospitals Case Medical Center, Cleveland, OH, United States, 3Department of Anatomic Pathology, University Hospitals Case Medical Center, Cleveland, OH, United States, 4Department of General Surgery, University Hospitals Case Medical Center, Cleveland, OH, United States, 5Department of Radiology, University Hospitals Case Medical Center, Cleveland, OH, United States
Synopsis
Pre-operative
planning in colorectal cancer is highly dependent on extent of tumor into the
mesorectum, but tumor margin is currently only assessed on excised pathology. Radiomic
features may capture subtle microarchitectural changes on a restaging MRI,
enabling characterization of tumor extent prior to surgery, even when residual
disease may not be visually discernible. We present
preliminary results for identifying radiomic features which discriminate
invasive from noninvasive tumor on a 3 Tesla restaging T2w MRI in colorectal
cancer. In a cohort of 24 patients, multi-scale gradient (Gabor) radiomic
features demonstrated high accuracy in segregating patients with invasive colorectal
cancer.Purpose
For patients with colorectal cancer, surgical
resection (typically following down-staging chemotherapy) is the only curative
therapy available [1]. Pre-operative planning in colorectal cancer is highly
dependent on invasion of tumor into the mesorectum and perirectal fat [2]. However,
the measure of tumor distance to the mesorectal wall (circumferential resection
margin, CRM) is only measured until after surgery, delaying adjuvant
intervention which could ensure better patient outcome. CRM values are
classified as either positive (if the tumor is within 1 mm of the mesorectal
wall) or negative (if the tumor localized to the mesorectum). Using a restaging
MRI alone to identify extent of tumor invasion is difficult,
as experts may not be able to accurately identify extent of tumor versus confounding
treatment effects
in vivo. Radiomic
features, or computer-extracted attributes from
radiographic images, have shown promise in quantifying subtle
microarchitectural differences between different tissue regions, potentially
enabling more accurate characterization of tumor extent after chemoradiation,
but prior to surgery [3]. We present preliminary results of our approach for
identifying radiomic features predictive of tumor invasiveness on a restaging
MRI in colorectal cancers.
Methods
24 patients
diagnosed with colorectal cancer were imaged using an axial T2-weighted (T2w) turbo-spin
echo MRI sequence post-neoadjuvant chemotherapy and prior to surgery. A total
of 78 first-order statistical, gray level, gradient, Haralick, and multi-scale
oriented Gabor radiomic feature maps were extracted from entire T2w volumes on
a per voxel basis in order to capture structural homogeneity and heterogeneity
characteristics within the region of tumor [4,5]. Expert annotations of the
tumor were made on the original T2w images. Our approach consisted of two
modules: (1) identifying top radiomic features by correlating feature
statistics (median, variance, kurtosis, skewness) with the ratio of
carcinoembryonic antigen (CEA) levels measured pre- and post-treatment, and (2)
performing principal component analysis (PCA) to calculate the optimal
combination of these top features in discriminating between patients who were
identified following surgical resection as having either a positive or negative
CRM. A cohort of 14 patients were used
for training purposes to score the radiomic features, and a separate cohort of
10 patients were used to test the top 10 features in discriminating between
positive and negative CRM classes (size of cohorts were limited due to
available clinical information).
Results and Discussion
In our testing cohort of 10 patients, 5 were
identified as having a positive CRM post-surgery (tumor within 1 mm of the
mesorectal wall), and 5 patients were identified as having a negative CRM
(tumor localized to the mesorectum). A
scatterplot of samples in 3D PCA space appears to demonstrate excellent
clustering of patients with positive and negative CRM with an accuracy of 90%
(one misclassification). While the original T2w intensity between images of
positive and negative CRM patients does not visually indicate marked differences
between the two patients, a heat-map of a top-ranked Gabor feature demonstrates
feature expression levels that are markedly different between positive and
negative CRM patients at the voxel level. Boxplots of feature intensities
between the two CRM classes further indicate that Gabor features express
differentially between positive and negative CRM patients, by capturing
multi-scale gradient information that may be reflective of tumor invasiveness.
Concluding Remarks
We have presented initial results of a quantitative
approach to predict tumor invasiveness using radiomic features in the context
of colorectal cancer, via restaging MR images. Gabor
features were found to be most discriminatory, by capturing microarchitechtural
oriented gradient differences between patients with positive and negative CRMs. Validation of these features on a larger cohort
of patients will enable us to develop a novel radiomic score for predicting
patient CRM class prior to surgery, allowing for better pre-operative surgical
planning.
Acknowledgements
Research reported in this publication was supported by the National Cancer Institute of the National Institutes of Health under award numbers R21CA167811-01, R21CA179327-01, R21CA195152-01, U24CA199374-01the National Institute of Diabetes and Digestive and Kidney Diseases under award number R01DK098503-02, the DOD Prostate Cancer Synergistic Idea Development Award (PC120857); the DOD Lung Cancer Idea Development New Investigator Award (LC130463),the DOD Prostate Cancer Idea Development Award; the Ohio Third Frontier Technology development Grant, the CTSC Coulter Annual Pilot Grant, the Case Comprehensive Cancer Center Pilot Grantthe VelaSano Grant from the Cleveland Clinicthe Wallace H. Coulter Foundation Program in the Department of Biomedical Engineering at Case Western Reserve University.References
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