Preoperative radiological staging of rectal cancer

Abstract

Rectal cancer is a common malignant disease that continues to have a highly variable outcome, with local recurrence after surgical resection usually leading to an incurable disease. Local recurrence is dependent upon tumor stages and surgical techniques. There is no general consensus on the role of transrectal ultrasonography (TRUS), computed tomography (CT), and magnetic resonance imaging (MRI) in staging of rectal cancer. The role of preoperative imaging is to determine which therapy may be suitable for the patients by surgery alone or with additional treatment. Although the tumor stage is an important prognostic factor, the evaluation of the involvement of the mesorectal fat and mesorectal fascia is even more important. New developments in techniques such as coils, sequences, and gradients in MRI, and evolution of multidetector CT (MDCT) allow better diagnostic options for patients with rectal cancer. Highresolution MRI has proved useful in clarifying the relationship between the tumor and the mesorectal fascia, representing circumferential resection margin at total mesorectal excision. At present, MRI is superior to CT or TRUS for assessing the local staging of rectal cancers. However, nodal staging remains a difficult radiological diagnosis. The role of MDCT has to be set, but for distant metastatic disease it remains to be the first option. This review discusses on the current role of the various imaging modalities in preoperative staging of the rectal cancer.