Cross-sectional imaging for local staging of rectal cancer

Cross-sectional imaging plays a key role in the local staging of rectal cancer. The two main goals of imaging are to classify patients into differentiated tumour risk profiles for neoadjuvant treatment stratification and to provide an anatomical roadmap of the tumour for detailed planning of the surgical resection strategy. In many countries, MRI is considered the modality of the first choice for local staging of rectal cancer. Strengths of MRI include its ability to accurately stratify high-risk T3 and T4 tumours and to assess tumour invasion into important surgical landmarks including the mesorectal fascia and anal sphincter. CT should only be considered as an alternative for local staging in upper rectal tumours (close to the rectosigmoid junction) or in case of limited availability or contraindications for MRI. Restaging with imaging has recently gained clinical significance due to the shift in treatment towards organ-preserving treatments for patients that respond very well to neoadjuvant treatment. In this setting, use of anatomical MRI to detect and stage any residual tumour is limited by the presence of fibrosis, and the addition of functional imaging (diffusion-weighted MRI) helps to improve the performance of MRI.