Abstract
Colorectal cancer is a type of cancer with increasing frequency, especially in developed countries. The stage of the disease at diagnosis is directly related to the prognosis, and the treatment approach is shaped by accurate staging. Magnetic resonance imaging (MRI) is prominent in evaluating the primary tumor due to its high soft tissue contrast. Although the sensitivity and specificity of fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) are reported to be higher than those of CT, its accuracy is limited by benign colonic involvements and inflammation-related involvements. While its sensitivity remains low in nodal staging, mostly due to the resolution limit, its superiority over conventional methods in detecting distant metastases has been reported. FDG PET/CT has been shown to detect recurrence with very high accuracy, even in patients with low carcinoembryonic antigen levels at restaging. There are studies investigating the role of FDG PET/CT in predicting the pathological response to neoadjuvant therapy in many patients with rectal cancer, and diffusion-weighted MRI has generally been found to be superior. To overcome the current limitations of FDG PET/CT, new generation imaging methods such as fibroblast activation protein inhibitor PET are being developed.