Clinical Staging of Rectal Cancer

Initial accurate clinical staging of patients with rectal cancer is necessary in order to select optimal treatment and determine prognosis. Decision-making for the best possible treatment is predicated on achieving the highest rate of cure while maintaining acceptable quality of life and avoiding unnecessary morbidity. Surgical options and indications for combined modality therapy will differ significantly, however, depending on tumor stage. Staging is based on depth of invasion of the rectal wall by tumor (T-stage) and presence of lymph node involvement (N-stage). Digital rectal examination (DRE), computed tomography (CT), magnetic resonance imaging (MRI), and endorectal ultrasound (ERUS) have all been used in local staging of rectal cancer. In the hands of an experienced clinician, the currently available technology can satisfactorily determine T-stage; however, prediction of N-stage is less reliable. This review discusses and compares the indications for, and advantages and limitations of, the various diagnostic modalities used in clinical staging of rectal cancer, with emphasis on ERUS and MRI. These two modalities have shown a similar accuracy in overall tumor staging. MRI seems to be more accurate in assessment of T3 and T4 lesions, whereas ERUS may be more accurate in assessment of T1 and T2 lesions. ERUS is faster, portable, more accessible and less expensive. MRI provides a multiplanar and larger field of view, capable of encompassing the entire mesorectal fascia and assessing the possibility of obtaining a tumor-free circumferential resection margin. Both modalities show moderate accuracy in predicting nodal disease.