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Objectives: To evaluate the diagnostic performance of whole-body MRI (WB-MRI) including contrast-enhanced T1-weighted imaging (T1WI) and WB-DWI in rectal cancer initial staging. Methods: This retrospective study was approved by the IRB and the requirement of informed consent was waived. From September 2013 to Feb 2015, patients who underwent rectal MRI including WB-MRI, as well as chest and abdominopelvic CT for initial staging, were included. WB-MRI consisted of contrast-enhanced T1-weighted imaging and DWI covering neck to the pelvis. Three radiologists reviewed WB-MRI and CECT independently for the M-classification. The diagnostic performance of CECT and WB-MRI was compared using a reference standard incorporating histology, FDG-PET results, and clinical follow-up. Results: A total of 139 patients (male:female = 89:50, mean age 63.2 ± 12.4 years) were included and metastasis was observed in 15.2% (21/139). WB-MRI showed significantly higher specificity (96.7% [114/118] vs. 85.6% [101/118], p = 0.001) and positive predictive value (PPV) (80% [16/20] vs. 48.5% [16/33], p < 0.001) than CECT. However, there were no significant differences in sensitivity (76.2% [16/21] for both, p > 0.99) and negative predictive value (95.3% [101/106] at CECT vs. 95.8% [114/119] at WB-MRI, p = 0.77) between CECT and WB-MRI. Conclusions: WB-MRI showed higher specificity and PPV than CECT in newly diagnosed rectal cancer. Adding WB-MRI to standard rectal MRI is a feasible option for initial staging workup of rectal cancer. Key Points: • WB-MRI showed a higher specificity and PPV than those of CECT for identifying metastasis at initial staging workup of rectal cancer. • WB-MRI and CECT did not show a significant difference in sensitivity and NPV for the M-classification. • WB-MRI can be used as an alternative to CECT for the initial M-classification modality in newly diagnosed rectal cancer. [ABSTRACT FROM AUTHOR]

Preoperative chemoradiotherapy is known to reduce the local recurrence of locally advanced rectal cancer. However, the careful use of preoperative chemoradiotherapy is essential, because unnecessary over‐treatment can result in unintended complications. Therefore, a diagnostic system for distinguishing between T2 and T3 rectal cancers should be developed. According to the diagnostic criteria for rectal cancer, radiologists first identify the locations and the shapes of both the tumor and the rectum from a medical image and then diagnose the T2/T3 rectal cancer by determining whether the tumor passes through the rectal wall or not. We construct two distinct convolutional neural network models to achieve the automated segmentation of each rectum and tumor, respectively. Then, we construct another convolutional neural network model, which uses the output images of segmentation models as input and determines whether the tumor in the input magnetic resonance image is at the T2 stage or at the T3 stage. We evaluate the effectiveness of the proposed method based on 290 magnetic resonance images from 133 subjects. The proposed model demonstrates an accuracy of 94%. [ABSTRACT FROM AUTHOR]

Objectives: This study was conducted in order to determine the prognostic value of MRI for extramural venous invasion (EMVI) in rectal cancer compared to pathology and to assess the diagnostic performance of multireaders.Methods: We retrospectively enrolled 222 patients (M:F = 148:74; mean age ± standard deviation, 61.5 ± 12 years) with histopathologically proven rectal cancers who underwent preoperative MRI between 2007 and 2016. Among them, 74 patients had positive EMVI on pathology (pEMVI) and 148 patients had negative pEMVI. Three radiologists with 7 (reviewer 1), 3 (reviewer 2), and 1 (reviewer 3) year of experience in rectal MR imaging determined the presence of EMVI on MRI (mrEMVI) using a 5-point grading system. Using histopathologic results as the reference standard, radiologists' performances were analyzed and compared with receiver operating characteristic (ROC) analysis. For assessment of interobserver variation, intraclass correlation coefficients (ICC) were used. Lastly, Kaplan-Meier estimation and Cox proportional hazard models were used for survival analysis.Results: The area under the ROC curve (AUC) was highest in reviewer 1 (0.829), followed by reviewer 2 (0.798) and reviewer 3 (0.658). Differences in AUCs between reviewer 1 or 2 and reviewer 3 were statistically significant (p < 0.001). ICC was substantial between reviewers 1 and 2. Overall survival (OS) was significantly different according to the positive circumferential resection margin, adjuvant treatment, and the presence of mrEMVI, but not by the presence of pEMVI.Conclusions: For experienced radiologists, the diagnostic performance of mrEMVI was good, resulting in better prediction of OS than with pEMVI, with substantial interobserver agreement.Key Points: • When read by experienced radiologists, MR can provide reliable diagnostic performance in assessing EMVI for patients with rectal cancer. • Positive mrEMVI is an adverse prognostic factor of overall survival and may influence the clinical decision-making. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the predictive factors for lateral pelvic lymph node (LPLN) metastasis in patients with locally advanced rectal cancer treated with preoperative chemoradiotherapy (CRT). Materials and methods: Fifty-seven patients with locally advanced rectal cancer and LPLNs larger than 5 mm underwent LPLN dissection (LPLD) after preoperative CRT. The MRI findings, including the apparent diffusion coefficient value and LPLN size reduction rate before/after CRT; clinical factors; and pathologic results were evaluated to identify the predictive factors associated with LPLN metastasis. Results: LPLN metastasis was confirmed in 23 patients (40.4%). Metastasis was significantly higher in LPLNs with multiplicity, short-axis diameter ≥8 mm before CRT, short-axis diameter >5 mm after CRT, size reduction rate ≤33.3%, heterogeneous signal intensity, and irregular margin (P<0.05) on MR. Multivariable analysis showed that pre-CRT short-axis diameter of LPLNs ≥8 mm, size reduction rate ≤33.3%, and heterogeneous signal intensity were independently associated with LPLN metastasis. Conclusions: The size and signal intensity of LPLN before and after CRT are useful MRI findings to predict LPLN metastasis and are helpful to determine the indications for LPLD. [ABSTRACT FROM AUTHOR]

Abstract Background Lateral pelvic node metastasis is one of the major causes of local recurrence in advanced rectal cancer after preoperative chemoradiotherapy (CRT). However, lateral pelvic node dissection (LPND) is still a challenging surgical procedure in terms of surgical morbidity. This study aimed to investigate the feasibility and safety of LPND in patients with advanced rectal cancer after preoperative CRT. Materials and methods Records of 80 consecutive patients who underwent total mesorectal excision (TME) with LPND for initially enlarged lateral pelvic nodes (LPNs) (short-axis diameter ≥5 mm on magnetic resonance imaging before preoperative CRT) between 2011 and 2016 were retrospectively reviewed. Surgical outcomes of these patients were compared with those of 281 patients who underwent TME alone. Results Ninety-nine LPND procedures were performed, including 19 bilateral LPNDs. Pathologically proven LPN metastasis was identified in 32 (32.3%) LPND cases after preoperative CRT. Multiple (odds ratio = 12.908, 95% confidence interval: 3.355-49.660, P < 0.001) and persistently enlarged LPNs (odds ratio = 27.093, 95% confidence interval: 6.072-120.896, P < 0.001) were independently associated with LPN metastasis. The rates of overall postoperative 30-d morbidity (42.5% versus 32.4%, P = 0.093) and urinary retention (11.3% versus 7.1%, P = 0.230) were similar between the TME with LPND and TME-only groups. Conclusions The postoperative morbidity of TME with LPND was comparable with TME-only group. The rate of LPN metastasis remained high after preoperative CRT, especially in patients with multiple or persistently enlarged LPNs. [ABSTRACT FROM AUTHOR]