Surgical Management of Colon Cancer

Malignant Polyps

• Complete endoscopic polypectomy is preferred should the morphological structure of the polyp allow
• Resection is recommended in the presence of the following unfavorable histological features:
  • Grade 3 or 4 differentiation
  • Level 4 invasion (invasion of the submucosal bowel wall below the polyp)
  • Venous or lymphatic invasion
  • Positive margin of resection (presence of tumor within 1-2 mm of the transected margin)

• In patients with pedunculated or sessile polyps with invasive carcinoma that has been completely resected and with favorable histologic features (clear resection margins, grade 1 or 2 lesions and no angiolymphatic invasion), observation may be considered without the additional surgery or colectomy
• Colectomy with en bloc removal of the lymph nodes is recommended for all polyps which are fragmented, with unfavorable histologic features and if margins cannot be assessed
• Total colonoscopy with follow-up surveillance colonoscopy is indicated in all patients who have resected polyps to rule out other synchronous polyps

Localized Disease

Colectomy with En Bloc Removal of Lymph Nodes

• Goal of surgery is to do wide resection of the involved segment of bowel including the removal of its lymphatic drainage
  • To be considered curative, resection needs to be complete
  • Resection should include a segment of the colon of at least 5 cm on either side of the tumor
  • Consider more extensive colectomy for those with strong family history of colon cancer or those <50 years of age

• Extent of colonic resection is determined by the tumor location, blood supply and regional lymph node distribution
  • At least 12 lymph nodes must be resected to clearly define stage II from stage III and to determine and prevent potential lymph node metastases
  • Suspicious clinically positive lymph nodes outside the area of resection should be biopsied or removed, if possible

• Obstructive tumors can be treated in 1 or 2 stages
  • Two-stage procedures include colostomy followed by colonic resection, or Hartmann’s procedure followed by colostomy closure and anastomosis (diversion followed by colectomy)
  • One-stage procedure is done with either subtotal colectomy and ileorectal anastomosis (resection with diversion), or in selected cases, intraoperative colonic lavage followed by segmental resection

• Laparoscopic colectomy may be considered if the following criteria are met:
  • Surgeon must be technically experienced in conducting laparoscopic colorectal surgeries
  • Disease must not be locally advanced
  • Preoperative marking of lesions must be considered
  • No acute bowel perforation, abdominal adhesions or obstruction from cancer
    • If found to have adhesions during laparoscopy, procedure should be converted to open surgery

Surgical Management of Rectal Cancer

• Aim to treat with the lowest possible risk of residual disease in the pelvis
  • Relatively high risk of locoregional recurrence due to close proximity of the rectum with pelvic structures and organs

• Sphincter and genitourinary functions should be preserved

Malignant Polyps

• Malignant rectal polyps refer to those which have invaded the muscularis mucosa and submucosa
• Completely resected polyps (pedunculated and single specimen sessile) with favorable histologic features and clear margins, observation may be considered without additional surgery
• Rectal surgery is recommended for all polyps with unfavorable histologic features (grade 3 or 4, with angiolymphatic invasion, positive margin of resection)
  • Transanal excision or transabdominal resection for polyps with fragmented specimen or margins that cannot be assessed
  • Transabdominal resection in those with unfavorable pathologic features to include lymphadenectomy

Localized Resectable Rectal Cancer

Endoscopic Mucosal Resection (EMR)

• Involves endoscopic snare resection of gastrointestinal tumors >2 cm in diameter located in the mucosal layer

Endoscopic Submucosal Dissection (ESD)

• An endoscopic procedure that involves en bloc resection of large submucosal gastrointestinal tumors by using a specialized dissecting knife

Transanal Excision

• Appropriate for selected early-stage cancers (T1, N0)
• For <3 cm, well to moderately differentiated tumors within 8 cm of the anal verge and <30% of the bowel circumference, with clear margin (>3 mm), without nodal involvement or evidence of lymphadenopathy on pretreatment imaging, mobile/nonfixed, and without lymphovascular or perineural invasion (PNI)
• For endoscopically removed polyp with cancer or indeterminate pathology
• Disadvantages include absence of pathologic staging for nodal metastases
  • Lymph node micrometastases are common in early rectal cancers and are likely to be missed by endorectal ultrasound

Transanal Endoscopic Microsurgery (TEM)

• May be done when the lesion can be adequately identified in the rectum
• May be technically feasible for more proximal lesions

Transabdominal Resection

• For those that cannot be managed with local resection
• Low anterior resection or abdominoperineal resection or coloanal anastomosis using total mesorectal excision
• Total mesorectal excision is recommended
  • Involves en bloc removal of the mesorectum, including angiolymphatic structures, mesorectal fascia and fatty tissues
  • If possible, biopsy or remove clinically suspicious nodes beyond the field of resection
  • In the absence of clinically suspicious nodes, extended resection is not necessary
  • Low anterior resection (LAR) extended 4-5 cm below the distal edge of the tumors followed by colorectal anastomosis creation is the procedure of choice for tumors located in the mid to upper rectum

• Done 5-12 weeks after 5.5 weeks of full-dose neoadjuvant chemoradiation
  • May be done at 3-7 days or 4-8 weeks after short-course neoadjuvant chemoradiation
• Digital rectal exam with or without a rigid or flexible endoscopy is needed to assess the distal margin prior to initiating this procedure; preoperative assessment of anticipated circumferential margins using MRI or prior to initiation of neoadjuvant therapy should be considered

Laparoscopic Surgery

• May be considered if the following criteria are met:
  • Conducted by an experienced surgeon
  • Thorough abdominal exploration is included
  • Limited to lower-risk tumors

T4 Lesions and/or Locally Unresectable Rectal Cancer

• Resection should be considered following preoperative chemoradiotherapy (chemoradiotherapy) unless with a clear contraindication
  • If surgery is contraindicated following primary treatment, patients should be given chemotherapy regimen for advanced or metastatic diseases

Surgical Management of Metastatic Colorectal Cancer

• Most treatment recommendations both apply to liver and lung metastases
• Complete resection based on anatomic location and extent of disease with maintenance of adequate function is required
  • Resection must be done with curative intent, either by one operation or a staged approach

• Hepatic resection is the management of choice for resectable hepatic metastases from CRC 
• Re-resection of hepatic and lung metastases can be considered in select patients
• Re-evaluation for resection and ablation should be considered in unresectable patients after 2 months of preoperative chemotherapy and every 2 months thereafter
• Evidence supporting resection of extrahepatic metastases remains limited