• Colorectal cancer is second commonest cancer causing death in the UK
• 20,000 new cases per year in UK - 40% rectal and 60% colonic
• 3% patients present with more than one tumour (=synchronous tumours)
• A previous colonic neoplasm increases the risk of a second tumour (=metachronous tumour)
• Some cases are hereditary
• Most related to environmental factors - dietary red fat and animal fat

Adenoma - carcinoma sequence

• Of all adenomas - 70% tubular, 10% villous and 20% tubulovillous 
• Most cancers believed to arise within pre-existing adenomas
• Risk of cancer greatest in villous adenoma
• Series of mutations results in epithelial changes from normality, through dysplasia to invasion
• Important genes - APC, DCC, k-ras, p53.

Clinical presentation

• Right-sided lesions present with
  • Iron deficiency anaemia due occult GI Blood loss
  • Weight loss
  • Right iliac fossa mass
• Left-sided lesions present with
  • Abdominal pain
  • Alteration in bowel habit
  • Rectal bleeding
• 40% of cancers present as a surgical emergency with either obstruction or perforation
• Emergency presentation is associated with a poorer outcome

Picture supplied by Mr N P J Cripps, Consultant Colorectal Surgeon, Chichester, United Kingdom

Picture provided by Mr David Anderson, St John's Hospital, Livingston, Scotland

Investigation

• In elective cases diagnosis can be confirmed by a combination of:
  • Rigid sigmoidoscopy
  • Flexible sigmoidoscopy
  • Colonoscopy
  • Double contrast barium enema
• In patients presenting with large bowel obstruction single contrast enema (after rigid sigmoidoscopy) is the investigation of choice

Surgical options

• Any surgical resection requires 5 cm proximal and  2 cm distal clearance for colonic lesions
• 1 cm distal clearance of rectal lesions adequate if mesorectum resected
• Radial margin should be histopathologically free of tumour if possible
• Lymph node resection should be performed to the origin of the feeding vessel
• En Bloc resection of adherent tumours should be performed
• The value of a 'no-touch' techniques remains unproven
• Depending on site of lesion surgical options are:
  • Caecum, ascending colon, hepatic flexure – Right hemicolectomy
  • Transverse colon – Extended right hemicolectomy
  • Splenic flexure, descending colon – Left hemicolectomy
  • Sigmoid colon – High anterior resection
  • Upper rectum – Anterior resection
• Consider defunctioning loop ileostomy is anastomosis <12 cm from anal margin
  • Lower rectum – Abdomino-perineal resection
  • Small lower rectal cancers may be resectable by transanal microsurgery
• Laparoscopic surgery is unproven
• Early studies raised concerns about port site recurrence
• Recent studies suggest equivalent overall and disease-free survival

Surgery for upper rectal cancers

• Risk of local recurrence reduced by performing total mesorectal excision (TME)
• Pelvic peritoneum and lateral ligaments divides
• Plane between visceral (rectum, mesorectum) and somatic structures dissected

• Middle rectal vessels divided laterally
• Rectal stump washed out with cytocidal fluid (water, Betadine) from below.

Picture provided by Prof Ian Bradford, Prince of Wales Hospital, Shatin, Hong Kong

Dukes Classification

• Developed by Cuthbert Duke in 1932 for rectal cancers
• Dukes staging of colorectal cancer

• Stage A - Tumour confined to the mucosa
• Stage B - Tumour infiltrating through muscle
• Stage C - Lymph node metastases present
• Five year survival - 90%, 70% and 30% for Stages A, B and C respectively

Adjuvant radiotherapy

• In patients with rectal cancer 50% undergoing curative resection develop local recurrence
• Median survival with local recurrence is less than one year
• Risk factors for local recurrence include:
  • Local extent of tumour
  • Nodal involvement
  • Circumferential margin status
• Risk of local recurrence can be reduced by radiotherapy
• Can be given either preoperatively or postoperatively
• Preoperative radiotherapy given as short course immediately prior to surgery
  • Reduces local recurrence
  • Increases time to recurrence
  • Improves 5-year survival
• Combination chemotherapy and radiotherapy may produce better outcome

Adjuvant chemotherapy

• Improves survival in Duke's C tumours
• Not required in Duke's A tumours which already have a good prognosis
• Role in Duke's B tumours remains to be defined
• Currently being investigated in the QUASAR (Quick and Simple and Reliable) trial
• Results of QUASAR study to date have shown
  • 5FU and folinic acid is effective as adjuvant therapy
  • High dose folinic acid rescue confers no additional benefit
  • The use of levimasole confers no additional benefit

Colorectal cancer screening

• Screening for colorectal cancer can be divided into two categories
  • Screening of high risk groups
  • Population screening

Screening of high risk groups

• This includes
  • Patients with family history
  • Sporadic adenomatous polyps
  • Inflammatory bowel disease
• Definition of the high risk group is difficult
• High risk patients should undergo colonoscopy at approximately 50 years
• Patients with family history of FAP or HNPCC should undergo genetic testing
• If mutation present should undergo intensive colonoscopic screening from adolescence

Population screening

• The role of screening is currently being investigated by either
  • Faecal occult blood testing
  • Colonoscopy
• Nottingham study has recruited over 150,000 patients
• 75,250 underwent biennial FOB testing
• Resulted in 1774 colonoscopies
• Seven complications occurred requiring operations in 6 patients
• No difference identified in stage of presentation in screened group
• Survival in screened group was significantly improved

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