colorectal%20cancer
COLORECTAL CANCER
Colorectal cancer is a carcinoma arising from the luminal surface of the colon.
It is the 2nd most common cancer in women and third most common cancer in male worldwide. It commonly arises from adenomatous polyps.
It is strongly linked to age with 83% occurring in people ≥60 years old.
Rectal cancer is defined as cancerous lesions located within 12 cm of the anal verge.

Surgical Intervention

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 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 & with favorable histologic features (clear resection margins, grade 1 or 2 lesions & 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 & regional lymph node distribution
    • At least 12 lymph nodes must be resected to clearly define stage II from stage III & to determine & 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 & anastomosis (diversion followed by colectomy)
    • One-stage procedure is done with either subtotal colectomy & 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
    • Thorough abdominal exploration is required

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 & organs
  • Sphincter & genitourinary functions should be preserved

Malignant Polyps

  • Malignant rectal polyps refer to those which have invaded the muscularis mucosa & submucosa
  • Completely resected polyps (pedunculated & single specimen sessile) with favorable histologic features & 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 & <30% of the bowel circumference, without nodal involvement or evidence of lymphadenopathy on pretreatment imaging, & 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 & 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 & 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
  • A rigid proctoscopy is needed prior to initiating this procedure

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 &/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 & lung metastases
  • Complete resection based on anatomic location & 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
  • Re-resection of hepatic & lung metastases can be considered in select patients
  • Re-evaluation for resection should be considered in unresectable patients after 2 months of preoperative chemotherapy & every 2 months thereafter
  • Evidence supporting resection of extrahepatic metastases remains limited

Hepatic Arterial Infusion (HAI) Therapy

  • Involves placement of a hepatic arterial port or implantable pump during liver resection
    • Where subsequent infusion of chemotherapy directed to the liver metastases will be given
    • Limited by its potential for biliary toxicity & required technical expertise
  • Should be considered selectively & in institutions capable of this procedure

Transarterial Chemoembolization

  • Involves catheterization of hepatic artery, causing vessel occlusion with local chemotherapy
  • Use is still limited to clinical trials

Tumor Ablation

  • Eg cryoablation, electro-coagulation, microwave ablation, percutaneous ethanol injection, radiofrequency ablation (RFA) 
  • May be considered in those who cannot undergo resection due to comorbidity, location of metastases or an estimate inadequate organ volume post-resection
  • Is not a substitute for resection in those patients with resectable diseases

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