Radiomic features on T2w MRI to predict tumor invasiveness for pre-operative planning in colorectal cancer: preliminary results
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

[1] NCCN Clinical Practice Guidelines in OncologyTM: Rectal Cancer, 2016 v.1. [2] MERCURYStudyGroup (2006). Diagnotic accuracy of preoperative magnetic resonance imaging in predicting curative resection of rectal cancer: prospective observational study. British Medical Journal 333, 779. [3] Viswanath S, Toth R, Rusu M et al (2014). Identifying quantitative in vivo multi-parametric MRI features for treatment related changes after laser interstitial thermal therapy of prostate cancer. Neurocomputing 144, 13-23. [4] Agner SC, Soman S, Libfeld E, et al (2010). Textural kinetics: a novel dynamic contrast-enhanced (DCE)-MRI feature for breast lesion classification. J Digit Imaging 24, 445-463. [5] Haralick RM, Shanmugam K, and Dinstein I (1973). Texture features for image classification. IEEE Trans Sys Man Cybern 3(6), 610-621.

Figures

Figure 1: (a) Projection of top 3 PCA features into 3D space for 10 patients: blue circles and red squares represent positive and negative CRM patients, respectively, clustered and separated by ellipses. (b)(d) Original T2w images with annotation for a single patient from each group (top: positive CRM; bottom: negative CRM). (c)(e) heat-maps of top-ranked Gabor feature overlaid on the original T2w images. Blue indicates low feature expression, whereas red indicates high feature expression.

Figure 2: Boxplots of normalized feature intensities for top 3 features between positive CRM and negative CRM patients. The difference in intensity distributions between the two classes indicates that Gabor features appear to express different information between invasive and noninvasive colorectal cancer.



Proc. Intl. Soc. Mag. Reson. Med. 24 (2016)
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