Colorectal Cancer

Background/Epidemiology

• Most common cancer in the UK after breast and lung.  Second most common cause of cancer death.
• More common in older (>65) men

Risk factors/Aetiology

Colorectal cancer is multifactorial.

• Three types
  • Sporadic (95%); HNPCC (5%); FAP (<1%)
• Genetic predisposition is a strong risk factor.  Those with a family history are at much higher risk.
  • Hereditary adenomatous diseases of the colon e.g. FAP and HNCCS, increase the risk to up to 100% and 50%, respectively
• Environmental factors- namely diet rich in red meat and saturated fat, poor in fibre, folate and calcium
• Obesity, smoking, alcohol excess
• Inflammation of the bowel (e.g. IBD); diabetes; other cancer

Screening

• In Scotland, all patients between the ages of 50 and 74 years are invited for screening for bowel cancer
• A Cochrane review showed that bowel screening programmes decrease the risk of dying from colon cancer by 16%
• The screening programme is distributed by sending patients a Faecal Occult Blood (FOB) kit.
  • Collect samples of stool to check for microscopic and biochemical blood products in the stool
  • NB FOB does not diagnose colon cancer
    • 10 in 500 patients will have abnormal result.  Out of these patients, one will have cancer, others will have polyps or another benign source of bleeding, and one will be a false positive.
    • An abnormal result should be investigated further, ideally with colonoscopy

Presentation

• Presentation can depend on the site of the cancer
  • Right sided/Caecal cancers
    • Often picked up by screening early.
    • If not, they may present late with vaguer signs/symptoms e.g.
      • weight loss, anaemia, mild diarrhoea, mass in the RIF
  • Left sided/Sigmoid cancers
    • Often more apparent and usually presents earlier (if not detected early by screening)
      • Colicky pain, rectal bleeding, large bowel obstruction, change in bowel habit, tenesmus, mass in LIF
  • Rectal cancer
    • Often rectal bleeding and mucus discharge
• Symptoms of anaemia, change in bowel habit, and rectal bleeding
  • Any of these symptoms (particularly in people >60 years old) warrants further investigation
    • together, suspicion is high, and patients >40 should be referred immediately
  • more rarely jaundice, ascites and hepatomegaly may also be present (liver/peritoneal mets are common)
  • Any abdominal mass requires further investigation

Recommendations for referral

• Urgent referral (within 2 weeks)
  • patients > 40 years old, reporting rectal bleeding with a change of bowel habit towards looser stools and/or increased stool frequency persisting for 6 weeks or more
  • patients > 60 years old, with rectal bleeding persisting for 6 weeks or more without a change in bowel habit and without anal symptoms
  • patients > 60 years old, with a change in bowel habit to looser stools and/or more frequent stools persisting for 6 weeks or more without rectal bleeding
  • any patient presenting with a right lower abdominal mass consistent with involvement of the large bowel
  • any patient with a palpable rectal mass
  • unexplained iron deficiency anaemia in men or non-menstruating women (Hb < 11 g/dl in men, < 10 g/dl in women)

Investigations

• Colonoscopy should be offered to confirm the diagnosis
  • Flexible sigmoidoscopy can be used as an alternative in patients with comorbidity
    • NB Considering the similarities between the procedures and the difference in scope (sigmoidoscopy can detect around 60% of tumours), a colonoscopy should always be the preferred choice
    • CT colonography may also be used if scoping is not possible, however a biopsy is not possible with this investigation, limiting its helpfulness compared to colonoscopy
• FBC, U&Es, LFTs
  • Unexplained iron-deficient anaemia is a cause for referral in men of any age and in non-menstruating women
  • Liver USS should be done should there be any liver signs, symptoms or deranged LFTs
• Abdominal CT and MRI are crucial to do prior to surgery and will aid diagnosis in the absence of colonoscopy too

Staging

• Duke’s staging- NB TNM staging has largely superseded Duke’s staging

1.  Invasion into but not through the bowel wall (90% 5-year survival)
2. Invasion through the bowel wall but not involving lymph nodes (70% 5-year survival)
3. Involvement of lymph nodes (30% 5-year survival)
   1. local lymph nodes
   2. distal lymph nodes
4. Widespread metastases (<10% 5-year survival)

Management

• Surgery
  • Right hemicolectomy/left hemicolectomy/ sigmoid colectomy/ anterior resection/ AP resection
    • Laparoscopic or open
  • A note about which surgery
    • With most bowel operations, there is the option to resect and rejoin (anastomosis) or to ‘defunction’ to protect the distal section by joining the proximal section to the skin.  These can be temporary (usually loop stomas
      • Right hemicolectomy for caecal tumours (even obstructing- but not if septic)
      • Left hemicolectomy for left-sided colon tumours (distal transverse and descending colon)
      • Anterior resection (essentially the same portion removed as left hemicolectomy) for sigmoid tumours (high) and high rectal tumours (with total mesorectal excision)
        • For low rectal tumours (<5cm from the dentate line) it may be more appropriate to perform abdominoperoneal resection (although generally a level of <2cm is the cut off) or anterior resection + defunctioning stoma (loop colostomy)
        • For anal tumours, an abdominoperineal excision of the rectum is preferred with end colostomy
      • A Hartmann’s procedure is often used in the emergency situation for rectosigmoid tumours where the surgeon will not want to anastomose the two ends of bowel/rectum.  Therefore, there is an end colostomy and a rectal stump
• Radiotherapy and Chemotherapy
  • FOLFOX (Folinic acid/Fluorouracil/Oxaliplatin) then Irinotecan +/- further fluorouracil and folinic acid (FOLFIRI)

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