Rectal Cancer Treatment (PDQ®): Treatment - Health Professional Information [NCI] - General Information About Rectal Cancer
Clinical Evaluation and Staging
Accurate staging provides crucial information about the location and size of the primary tumor in the rectum, and, if present, the size, number, and location of any metastases. Accurate initial staging can influence therapy by helping to determine the type of surgical intervention and the choice of neoadjuvant therapy to maximize the likelihood of resection with clear margins. In primary rectal cancer, pelvic imaging helps determine the depth of tumor invasion, the distance from the sphincter complex, the potential for achieving negative circumferential (radial) margins, and the involvement of locoregional lymph nodes or adjacent organs. The initial clinical evaluation and staging procedures may include the following:[7,18,19,20,21,22,23]
- Digital-rectal examination and/or rectovaginal exam and rigid proctoscopy to determine if sphincter-saving surgery is possible.[7,18,19]
- Complete colonoscopy to rule out cancers elsewhere in the bowel.
- Pan-body computed tomography (CT) scan to rule out metastatic disease.
Magnetic resonance imaging (MRI) of the abdomen and pelvis to determine the depth of penetration and the potential for achieving negative circumferential (radial) margins, as well as to identify locoregional nodal metastases and distant metastatic disease.
- Endorectal ultrasound (ERUS) with a rigid probe or a flexible scope for stenotic lesions to determine the depth of penetration and identify locoregional nodal metastases.[19,21]
Positron emission tomography (PET) to image distant metastatic disease.
- Measurement of the serum carcinoembryonic antigen (CEA) level for prognostic assessment and the determination of response to therapy.[22,23]
In the tumor (T) staging of rectal carcinoma, several studies indicate that the accuracy of ERUS ranges from 80% to 95% compared with 65% to 75% for CT and 75% to 85% for MRI. The accuracy in determining metastatic nodal involvement by ERUS is approximately 70% to 75% compared with 55% to 65% for CT and 60% to 70% for MRI. In a meta-analysis of 84 studies, none of the three imaging modalities, including ERUS, CT, and MRI, were found to be significantly superior to the others in staging nodal status. ERUS using a rigid probe may be similarly accurate in T and regional lymph node (N) staging when compared to ERUS using a flexible scope; however, a technically difficult ERUS may give an inconclusive or inaccurate result for both T stage and N stage. In this case, further assessment by MRI or flexible ERUS may be considered.[21,25]