In addition to initial staging prognostic features, MRI response to neoadjuvant treatment has been shown to be an indicator of long-term outcomes, including recurrence and survival [48-51]. Reduced field of view diffusion-weighted images (DWI) may demonstrate better image quality than full field of view DWIs [52]. For lymph node involvement, the differentiation of benign from metastatic locoregional nodes remains challenging. MRI is sensitive for detecting enlarged lymph nodes but remains nonspecific for differentiating benign from malignant nodes with accuracies ranging from 59% to 83% [32,36,53,54]. However, studies have shown high negative predictive value in the setting of node-negative determination by MRI, with negative predictive value ranging from 78% to 87% [32,36,53,54]. In a study of 60 patients with rectal cancer, 68.3% of patients with nodal metastasis were correctly identified using a size threshold of 7.2 mm, and accuracy was not improved by morphologic criteria [55]. However, in a study of 52 patients with rectal cancer, prediction of N stage was improved Staging of Colorectal Cancer by considering dimension, morphology, and signal characteristics [56]. Standardized reporting systems and templates have been shown to result in more complete MRI reports [57]. US Pelvis Transrectal TRUS has been considered the reference standard for T-stage evaluation of rectal carcinoma with rich historical evidence to support its use. TRUS is able to differentiate the layers of the rectal wall and provides high accuracy in detecting and characterizing tumors within the superficial layers of the rectal wall. Reported accuracies range between 80% and 97% for T-stage determination [58]. The T-stage accuracy for TRUS (84.6%) is far superior to that of CT (70.5%) [23].
Staging of Colorectal Cancer. In addition to initial staging prognostic features, MRI response to neoadjuvant treatment has been shown to be an indicator of long-term outcomes, including recurrence and survival [48-51]. Reduced field of view diffusion-weighted images (DWI) may demonstrate better image quality than full field of view DWIs [52]. For lymph node involvement, the differentiation of benign from metastatic locoregional nodes remains challenging. MRI is sensitive for detecting enlarged lymph nodes but remains nonspecific for differentiating benign from malignant nodes with accuracies ranging from 59% to 83% [32,36,53,54]. However, studies have shown high negative predictive value in the setting of node-negative determination by MRI, with negative predictive value ranging from 78% to 87% [32,36,53,54]. In a study of 60 patients with rectal cancer, 68.3% of patients with nodal metastasis were correctly identified using a size threshold of 7.2 mm, and accuracy was not improved by morphologic criteria [55]. However, in a study of 52 patients with rectal cancer, prediction of N stage was improved Staging of Colorectal Cancer by considering dimension, morphology, and signal characteristics [56]. Standardized reporting systems and templates have been shown to result in more complete MRI reports [57]. US Pelvis Transrectal TRUS has been considered the reference standard for T-stage evaluation of rectal carcinoma with rich historical evidence to support its use. TRUS is able to differentiate the layers of the rectal wall and provides high accuracy in detecting and characterizing tumors within the superficial layers of the rectal wall. Reported accuracies range between 80% and 97% for T-stage determination [58]. The T-stage accuracy for TRUS (84.6%) is far superior to that of CT (70.5%) [23].