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]
In patients with rectal cancer, the circumferential resection margin (CRM) is an important pathological staging parameter. Measured in millimeters, it is defined as the retroperitoneal or peritoneal adventitial soft-tissue margin closest to the deepest penetration of tumor.
Although based on retrospective data, the American Joint Committee on Cancer and a National Cancer Institute-sponsored panel have recommended that at least 12 lymph nodes be examined in patients with colon and rectal cancer to confirm the absence of nodal involvement by the tumor.[26,27,28][Level of evidence: 3iiiA] This recommendation takes into consideration that the number of lymph nodes examined is a reflection of both the aggressiveness of lymphovascular mesenteric dissection at the time of surgical resection and the pathologic identification of nodes in the specimen. Retrospective studies have demonstrated that the number of lymph nodes examined in colon and rectal surgery may be associated with therapeutic outcome.[29,30,31,32] Staging studies may be required if recurrence or progression of disease is suspected; MRI may be particularly helpful in determining sacral involvement in local recurrence.
Due to the increased risk of local recurrence and a poorer overall prognosis, the management of rectal cancer varies somewhat from that of colon cancer. Differences include surgical technique, the use of radiation therapy, and the method of chemotherapy administration. In addition to determining the intent of rectal cancer surgery (i.e., curative or palliative), it is important to consider therapeutic issues related to the maintenance or restoration of normal anal sphincter, genitourinary, and sexual functions.[25,33] The approach to the management of rectal cancer should be multimodal and should involve a multidisciplinary team of cancer specialists with expertise in gastroenterology, medical oncology, surgical oncology, radiation oncology, and radiology.
The surgical approach to treatment varies according to the location, stage, and presence or absence of high-risk features (i.e., positive margins, lymphovascular invasion, perineural invasion, and poorly differentiated histology) and may include:[25,33,34]
- Polypectomy for select T1 cancers.
- Transanal local excision (LE) and transanal endoscopic microsurgery (TEM) for select clinically staged T1/T2 N0 rectal cancers.
- Total mesorectal excision (TME) with autonomic nerve preservation (ANP) techniques via low anterior resection (LAR).
- TME via abdominoperineal resection (APR) for patients who are not candidates for sphincter-preserving operations, leaving patients with a permanent end-colostomy.