Colorectal Cancer Learning Resource

Definition

  • Colorectal cancer (CRC) defines the spectrum of neoplastic diseases that arise in the colon (60%) or rectum (40%)
  • CRC is the second most common cancer in Ireland: accounts for 13% cancers in women and 15% in men (excludes non-melanomatous skin ca)

Risk factors

  • Increasing age
  • Male gender
  • Diets rich in meat and fat
  • Increased BMI
  • History of smoking
  • Personal previous history of CRC
    Personal history of colorectal polyps
  • Genetic disorders: Lynch syndrome, FAP, Peutz-Jegher
  • Inflammatory bowel disease

colon cancer learning resource

Presentation

LEFT-SIDED COLON CANCER/RECTAL CANCER RIGHT-SIDED COLON CANCER
Altered bowel habit Iron deficiency anaemia (insidious blood loss)
Rectal bleeding Weight loss
Abdominal pain Palpable mass
Emergency: obstruction/perforation (worse prognosis)

Investigation

  • Colonoscopy
    • Low rectal tumours can be diagnosed on sigmoidoscopy alone but approximately 3% of patients will have a second synchronous tumour
  • Staging CT TAP
  • FBC > check haemoglobin
  • Tumour markers: CEA

Treatment

Surgical options depends on the site of the lesion (blood supply)

LOCATION OPERATION
Right sided tumours:
Caecum/Ascending colon/Hepatic flexure
Right hemi-colectomy
Transverse colon Extended right hemicolectomy
Splenic flexure/descending colon Left hemi-colectomy
Sigmoid colon High anterior resection
Upper rectum Anterior resection (with TME)
Lower rectum Abdomino-perineal resection
  • Use of systemic neoadjuvant/adjuvant chemotherapy and neoadjuvant/adjuvant radiotherapy depends on stage and is decided after multidisciplinary discussion

 

Aetiology

  • The development of CRC arises as a result of sequential mutation of several tumour suppressor genes (TSG) and proto-oncogenes.
  • Two potential pathways depending on which TSG is inactivated.
    • APC gene inactivation – 85% of sporadic CRC (Vogelstein’s pathway, figure 1)
    • Mismatch repair gene instability – 15%.

Colorectal cancer study resource

 

TNM staging of colorectal cancer [1]

 

T-stage N-stage  M  
TX Cannot be assessed NX Cannot be assessed M0 No distant metastasis
T0 No evidence of tumour N0 No regional lymph node metastasis M1 Distant metastasis
Tis In-situ disease N1 Metastasis in 1-3 regional lymph nodes    
T1 Invasion of submucosa N2 Metastasis in 4 or more lymph nodes    
T2 Invasion of muscularis propria    
T3 Invasion into pericolic tissues    
T4a Penetrates visceral peritoneum    
T4b Invades other organs    
     

 

Duke’s staging [2]

Stage Definition Predicted 5-year survival
A Tumour confined to mucosa 90%
B Infiltration through muscle 70%
C Metastases to lymph nodes 30%

 

[1] AJCC Cancer Staging Manual (Sixth ed.). Springer-Verlag New York, Inc. 2002.

[2] Dukes C E. The classification of cancer of the rectum. J Pathol Bacteriol. 1932;35:323–332.

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