Colorectal Cancer Flashcards
Definition
• Malignant adenocarcinoma of the large bowel
o Distribution:
• 60% - rectum and sigmoid
• 30% - descending colon
• 10% - rest of colon
Dukes Classification
A - limited to muscularis mucosae - 93% 5yr survival rate
B - extension through muscularis mucosae -77%
C - involvement of regional lymp nodes - 48%
D - distant metastasis - 6.6%
Aetiology/risk factors
Environmental and genetic Genetic changes, epithelial dysplasia > adenoma > carcinoma involving accumulation of genetic changes in oncogenes and tumour suppression genes e.g. APC then COX2 over-expression then K-Ras then p53 Inherited conditions are associated with high rates of colorectal carcinoma e.g. FAP, HNPCC Risk Factors Western Diet Smoking Colorectal Polyps Previous colorectal cancer Family History IBD Chronic Bowel Inflammation
Epidemiology
SECOND MOST COMMON cause of cancer death in WEST
3rd most common in UK, 2nd most cause of deaths
UK: 20,000 deaths per year
Average age of diagnosis: 60-65 yrs
Symptoms
• Depends on the size and location of the tumour
• Left-Sided Colon and Rectum
o Change in bowel habit
o Rectal bleeding (blood or mucus mixed with the stools)
o Tenesmus (due to a space-occupying tumour in the rectum)
• Right-Sided Colon
o Presents later
o Anaemia symptoms (lethargy)
o Weight loss
o Non-specific malaise
o Lower abdominal pain (rare)
• IMPORTANT: 20% of tumours will present as an EMERGENCY with pain and distension due to:
o Large bowel obstruction
o Haemorrhage or peritonitis due to perforation
Signs on PE
• Anaemia • Abdominal mass • If metastatic: o Hepatomegaly o Ascites (shifting dullness) • Low-lying rectal tumours may be palpable on DRE
Investigations
• Bloods o FBC - anaemia o LFTs o Tumour markers (CEA) • Stools o FOBT - used as a screening test • Endoscopy o Sigmoidoscopy o Colonoscopy o This can be used to biopsy the tumour • Double-Contrast Barium Enema o May show 'apple core' strictures • Contrast CT o Abdominal ultrasound for hepatic metastases o For staging (Duke's staging)
