Colorectal Carcinoma

Question 1

How common in colorectal carcinoma

Answer 1

3rd most common in world

2nd in UK

Question 2

Pathophysiology

Answer 2

1. Chromosomal instability caused oncogene and tumour suppressor gene mutation
2. Causes adenomatous polyposis coli (APC)
3. Epithelial dysplasia
4. Adenoma
5. adenocarcinoma

Question 3

Inheritance pattern of familial adenomatous polyposis (FAP)

Answer 3

Autosomal dominant

Question 4

Pathophysiology of FAP

Answer 4

Mutation of the APC gene which is a tumour suppressor gene that

• CpG island methylation phenotype - causes cytosine guanine clusters which silence tumour suppressor gene
• microsatellite instability - inactivated mismatch repair linked to Lynch syndrome (HNPCC) - usullay proximal colon

Question 5

Risk factors

Answer 5

Age 
FHx 
Chronic IBD 
Polyps 
Obesity, smoking, red meat 
Abdo radiotherapy

Question 6

Presentations

Answer 6

Rectal bleeding 
Change in bowel habits - diarrhoea, tenesmus, mucus 
FLAWS 
Abdominal pain
Right sided - iron deficiency anaemia 

20% emergency obstruction, haemorrhage, perforation causing peritonitis

Question 7

Examination

Answer 7

Abdo exam: signs caused by metastasise

• hepatomegaly
• ascites - shifting dullness
• palpable Abdo mass
• abdominal distension

Features of anaemia
MUST DO DRE - Abdo or rectal mass

Question 8

Clinical suspicion in GP setting management

Answer 8

FIT test to detect blood in stool

2 week wait referral

Question 9

Indications for 2ww

Answer 9

Positive FIT test
40+ with unexplained weight loss and Abdo pain
50+ and unexplained PR bleeding
60+ with IDA or change in bowel habits

Question 10

Investigations

Answer 10

Examination + DRE
Obs
Bloods - FBC (anaemia), Fe, CEA (if confirmed CRC)
FIT - blood in stool
Colonoscopy and biopsy
CT scan CAP for staging and large tumours
- barium swallow - apple core sign

If rectal cancer - MRI

Question 11

CEA

Answer 11

Carcinoembryonic antigen

Not specific or sensitive so only done after confirmed diagnosis and cannot be diagnostic

Question 12

Treatment

Answer 12

Surgical resection if localised
Chemotherapy as adjuvant therapy if later stage, used more for colon than rectal
Radiotherapy - rectal cancer with surgical resection

Question 13

BRAF V600E

Answer 13

More resistant to chemotherapeutic treatments

Question 14

Screening target audience

Answer 14

60 - 74 years old
In England from April 2021 - 50+ yo

Every 2 years

Question 15

Screening procedure

Answer 15

FIT kit test to be done at home

If positive, given colonoscopy

Question 16

HNPCC hereditary pattern

Answer 16

Hereditary non polyposis colon cancer

Autosomal dominant