Colorectal Carcinoma

Question 1

Define Colorectal Carcinoma and what are the types

Answer 1

Majority malignant adenocarcinomas of the large bowel, derived from epithelial cells

Adenocarcinoma (most common)
Carcinoid tumours
GI stromal tumours
Lymphomas

Question 2

Aetiology of Colorectal Carcinomas

Answer 2

Adenoma carcinoma sequence (arising from dysplastic adenomatous polyps)
Combination of genetic and environmental factors:
Genetic: FMHx, FAP, Lynch syndrome
Environmental: Obesity, high energy intake, reduced exercise and dietary fibre, increase intake of red and processed meat

Question 3

Where is the most common site of colorectal carcinoma

Answer 3

71% of new colorectal cancers arise in the colon and 29% arise in the rectum

Question 4

Risk factors for Colorectal Carcinoma

Answer 4

Increasing age (90% of cases >40)
Adenomatous polyposis coli mutation - FAP 
Lynch syndrome (HNPCC)
MYH-associated polyposis (MAP)
Hamartomatous polyposis syndromes (Juvenile polyposis, Peutz-Jegher's syndrome)
IBD - specifically UC
Obesity
Smoking 
Alcohol

Question 5

Symptoms of Colorectal Carcinoma

Answer 5

Asymptomatic in the early stages

Rectal bleeding (Mixed in the stool)
Change in bowel habit (Increased frequency, looser stools, L sided - combined with rectal bleeding)
Abdominal pain
Weight loss and anorexia (advanced disease)
Anaemia: fatigue, SOB,
Abdominal lump or distension (advanced disease due to ascites or intestinal obstruction)

FMHx

Question 6

Difference in presentation of a right vs left colorectal carcinoma

Answer 6

Right
Later presentation
Anaemia
Weight loss
Non-specific malaise
Lower abdominal pain

Left
Change in bowel habit
Rectal bleeding or blood/mucous mixed with stool
tenesmus

Question 7

Signs of Colorectal Carcinoma on examination

Answer 7

Rectal mass on DRE (L-sided)
Anaemia: conjunctival pallor (R-sided)
Abdominal mass (late)
Abdominal distensions (late)
 Palpable lymph nodes (late)
Metastases: shifting dullness, hepatomegaly

Question 8

What staging system is used for colorectal carcinoma

Answer 8

Duke’s staging
A: Confined to the mucosa

B1: Growth into the muscularis proposa
B2: growth through the muscularis proposa and serosa

C1: Spread to 1-4 regional lymph nodes
C2: Spread to >4 regional lymph nodes

D: Distant metastases (lung, liver, bone, brain)

Question 9

Investigations for Colorectal Carcinoma

Answer 9

Any systemic symptoms (weight loss etc.) or rectal bleeding >55 -> urgent 2 week referral

Sigmoidoscopy/colonoscopy + biopsy: ulcerating or exophytic mucosal lesion

Stool sample: Occult or frank blood
Faecal occult blood testing: positive

FBC: anaemia
LFTs: normal (even if mets)
Renal function (normal)
Tumour markers: CEA raised

Barium enema: colonic mass lesion and apple core lesion
CT colonography: ulcerating or exophytic mucosal lesion
CT CAP/PET: staging
Pelvic MRI: staging

Question 10

What is the screening for Colorectal Cancer

Answer 10

The NHS currently offers two types of screening:

1. Faecal occult blood test (FOBT) for men and women age 60-74 (every 2 years)
2. One-off flexible sigmoidoscopy for men and women at the age of 55.