___________________________________________________________________________ Colorectal Cancer
Low Risk • Clinical stage T1, T2 or T3a, AND • No lymph node involvement
Approximately 28% of colorectal malignancies are attributable to rectal carcinoma. Although surgical resection is the only curative option for rectal cancer, complete resection is rendered technically difficult by the lack of serosa covering the rectum and proximity of the rectum to the bony pelvis and other pelvic organs. Local tumor invasion is promoted by this extra- colorectal proximity to other organs, which, along with surgical difficulty, contributes to high local recurrence rates [187; 205]. Compared with colon cancer, the increased risk of local recurrence and poorer overall prognosis in rectal cancer has led to differences in the management of localized or locally advanced disease, including greater emphasis on multimodal treatment to minimize morbidity, decrease recurrence risk, and prolong survival [242]. Other differences in rectal cancer treatment include surgical techniques, use of radiation therapy, and chemotherapy protocol. In stage II or III rectal cancer, neoadjuvant therapy is now favored over adjuvant therapy based on evidence of improved local control and increased rates of sphincter preservation [243; 244; 245].
Moderate Risk • T3b or greater, in which the potential surgical margin is not threatened, OR • Any suspicious lymph node not threatening surgical resection margins, OR • The presence of extramural vascular invasion High Risk • A threatened (<1 mm) or breached resection margin, OR • Low tumors encroaching onto the inter-sphincteric plane or with levator involvement Primary Surgical Therapy Rectal cancer surgery involves surgical resection of the primary tumor. Surgical approach is guided by tumor location, disease stage, and presence of high-risk features (e.g., positive margins, lymphovascular invasion, perineural invasion, poorly differentiated histology) [205]. Polypectomy alone may be sufficient when polyps with invasive cancer can be completely resected with clear margins and show favorable histologic features, generally select T1 cancers [248]. Approaches with minimal morbidity and mortality include transanal excision and transanal endoscopic microsurgery. Local excision is appropriate in selected T1 tumors, with mesorectal excision preferred for all other T1–T2/N0 tumors. Endoscopic microsurgery cannot perform excision and staging of mesorectal lymph nodes, a limitation because T1 lesions have a 6% to 11% risk of harboring nodal metastasis [249]. Local recurrence rates range from 7% to 21% for T1 lesions and 26% to 47% for T2 lesions [249; 250; 251]. Total mesorectal excision with autonomic nerve preservation via low-anterior resection is preferred, followed by colorectal anastomosis in advanced mid- to upper-rectal tumor. Low anterior rectal resection is associated with bowel urgency, increased bowel frequency, clustering, and fecal incontinence from loss of rectum reservoir function. The colonic J-pouch is the superior approach for improving postoperative bowel function [59; 252]. In patients unsuitable for sphincter- preservation, total mesorectal excision via abdominoperineal resection is preferred, although this leaves patients with a permanent colostomy [253; 254; 255]. Total mesorectal excision has demonstrated reproducible reductions in local recurrence and improvement in disease-free and overall survival [256]. Despite the low rate of local relapse after meticulous mesorectal excision, the heightened tendency for first failure to solely occur in locoregional sites requires the ongoing routine use of adjuvant radiation therapy [187; 257].
The National Comprehensive Cancer Network recommends combined-modality therapy consisting of surgery, concurrent fluoropyrimidine-based chemotherapy with ionizing radiation to the pelvis, and chemotherapy for the majority of patients
with stage II or stage III rectal cancer. (https://www.nccn.org/professionals/physician_gls/pdf/ rectal.pdf. Last accessed March 14, 2022.) Level of Evidence : 2a (Based upon lower-level evidence, there is uniform NCCN consensus that the intervention is appropriate.) An important consideration is the impact of rectal cancer surgery on the structure and function of adjacent sensitive tissues, and the therapeutic issues related to the maintenance or restoration of normal anal sphincter, genitourinary, and sexual function [242; 246; 247]. Practice recommendations for the surgical treatment of localized rectal cancer have been published by the ASCRS ( Table 10 ) [187]. Treatment of rectal cancer is determined by clinical disease stage and the risk of local recurrence. Low-risk, early-stage disease is generally treated with primary surgical therapy, while locally advanced or high-risk disease requires multimodality therapy that includes neoadjuvant radiation or chemoradiation [187]. The risk of local recurrence is estimated using MRI imaging before surgical intervention. Risk level is defined as low, moderate, or high based on the following criteria [238]:
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