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Objectives: This study aimed to identify whether apparent diffusion coefficient (ADC) values and dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) parameters are helpful in distinguishing mesorectal tumor deposits (TD) from metastatic lymph nodes (MLN) in rectal cancer (RC). Methods: Thirty patients (59 lesions, including 30 TD and 29 MLN) with RC who underwent pretreatment-MRI between February 2016 and August 2018 were enrolled. The morphological features, ADC values, and semi-quantitative parameters of DCE-MRI, including relative enhancement (RE), maximum enhancement (ME), maximum relative enhancement (MRE), time to peak (TTP), wash-in rates (WIR), wash-out rates (WOR), brevity of enhancement (BRE), and area under the curve (AUC) were measured on lesions (TD or MLN) and RC. The parameters were compared between TD and MLN, tumor with and without TD group by using Fisher's exact test, independent-samples t-test, and Mann-Whitney U test. The ratio (lesion-to-tumor) of the parameters was compared between TD and MLN. Receiver operating characteristic curve analysis and binary logistic regression analysis were used to assess the diagnostic ability of single and combined metrics for distinguishing TD from MLN. Results: The morphological features, including size, shape, and border, were significantly different between TD and MLN. TD exhibited significantly lower RE, MRE, RE-ratio, MRE-ratio, ADCmin-ratio, and ADCmean-ratio than MLN. RE-ratio showed the highest AUC (0.749) and accuracy (77.97%) among single parameters. The combination of DCE-MRI and DWI parameters together showed higher diagnostic efficiency (AUC = 0.825). Conclusions: Morphological features, ADC values, and DCE-MRI parameters can preoperatively help distinguish TD from MLN in RC. Key Points: • DWI and DCE-MRI can facilitate early detection and distinguishing mesorectal TD (tumor deposits) from MLN (metastatic lymph nodes) in rectal cancer preoperatively. • TD has some specific morphological features, including relatively larger size, lower short- to long-axis ratio, irregular shape, and ill-defined border on T2-weighted MR images in rectal cancer. • The combination of ADC values and semi-quantitative parameters of DCE-MRI (RE, MRE) can help to improve the diagnostic efficiency of TD in rectal cancer. [ABSTRACT FROM AUTHOR]

Background: To investigate whether MRI findings, including texture analysis, can differentiate KRAS mutation status in rectal cancer.Methods: Totally, 158 patients with pathologically proved rectal cancers and preoperative pelvic MRI examinations were enrolled. Patients were stratified into two groups: KRAS wild-type group (KRASwt group) and KRAS mutation group (KRASmt group) according to genomic DNA extraction analysis. MRI findings of rectal cancers (including texture features) and relevant clinical characteristics were statistically evaluated to identify the differences between the two groups. The independent samples t test or Mann-Whitney U test were used for continuous variables. The differences of the remaining categorical polytomous variables were analyzed using the Chi-square test or Fisher exact test. A receiver operating characteristic (ROC) curve analysis was performed to evaluate the discriminatory power of MRI features. The area under the ROC curve (AUC) and the optimal cut-off values were calculated using histopathology diagnosis as a reference; meanwhile, sensitivity and specificity were determined.Results: Mean values of six texture parameters (Mean, Variance, Skewness, Entropy, gray-level nonuniformity, run-length nonuniformity) were significantly higher in KRASmt group compared to KRASwt group (p < 0.0001, respectively). The AUC values of texture features ranged from 0.703~0.813. In addition, higher T stage and lower ADC values were observed in the KRASmt group compared to KRASwt group (t = 7.086, p = 0.029; t = - 2.708, p = 0.008).Conclusion: The MRI findings of rectal cancer, especially texture features, showed an encouraging value for identifying KRAS status. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the diagnostic potential of DW-MRI relative parameters for differentiation of rectal cancers with different Kirsten rat sarcoma viral oncogene homologue (KRAS) mutation status.Methods: Fifty-one patients with rectal cancer underwent diffusion-weighted MR imaging with eight b values. ADCs (including Max-ADC, Min-ADC and Mean-ADC) and IVIM parameters (D, pure diffusion; f, perfusion fraction; D*, pseudodiffusion coefficient) were respectively calculated by mono- and bi-exponential analysis. Patients were stratified into two groups: KRAS wild type and mutant. The DW-MRI-derived parameters between the KRAS wild-type group and KRAS mutant group were compared using the Mann-Whitney U test. Receiver-operating characteristic (ROC) analysis of discrimination between KRAS wild-type and KRAS mutant rectal cancer was performed for the DW-MRI-derived parameters.Results: Max-ADC, Mean-ADC and D values were significantly lower in the KRAS mutant group than in the KRAS wild-type group, whereas a higher D* value was demonstrated in the KRAS mutant group. According to the ROC curve, Mean-ADC and D* values showed moderate diagnostic significance with the AUC values of 0.756 and 0.710, respectively. The cut-off values for Mean-ADC and D* were 1.43 × 10-3mm2/s and 26.58 × 10-3mm2/s, respectively.Conclusion: Rectal cancers had distinctive diffusion/perfusion characteristics in different KRAS mutation statuses. The DW-MRI-derived parameters, specifically Mean-ADC and D*, show a moderate diagnostic significance for KRAS status.Key Points: • Rectal cancers with different KRAS mutation statuses demonstrated distinctive diffusion/perfusion characteristics. • Max-ADC, Mean-ADC and D values were lower in the KRAS mutant group. • A higher D* value was demonstrated in the KRAS mutant group. • IVIM-DW MRI may potentially help preoperative KRAS mutant status prediction. [ABSTRACT FROM AUTHOR]