Colorectal Cancer Flashcards
Industrialisation and economic growth
Western dietary pattern, sedentary lifestyle and increasing obesity
Polyp
Non cancerous growth
Inner lining of colon/rectum
Starts off benign ; <10% turn cancerous
Can be removed during endoscopy
Long latent period of CRC progression —> screening and early detection
Signs and symptoms
Growth of tumour into lumen or adjacent structures
Early CRC: asymptomatic
Change in bowel habits
Bleeding from rectum ; blood in stools
Anaemia — weakness, fatigue
Stool more narrow
Prolonged constipation / diarrhoea
Decreased appetite
Weight loss
Risk factors
Increasing age
Male
Family history of CRC ; personal history of CRC and colorectal polyps
Familial adenomatous polyposis (FAP) — development of many colorectal polyps
Lynch syndrome
Smoking
Obesity
Chronic inflammatory bowel disease — Ulcerative colitis ; Crohn’s disease
Type II diabetes
Excessive alcohol
Poor diet — low fruits and veg ; high red/processed meat
Protective factors
Physical activity
Polypectomy — removal of polyps
Long term low-dose aspirin
CRC screening (50-79)
Stool based occult blood tests
Faecal immunochemical test (FIT)
Guanaco based faecal occult blood test
FIT-DNA
Direct visualization tests
Colonoscopy
Flexible sigmoidoscopy
CT colonography
gFOBT
Detect heme using chemical indicator (guaiac)
3 samples on consecutive days
Every yr
FIT
Immunochemical detection of Ab to globule portion of Hb
More sensitive and specific than gFOBT — not detect glob in from non-human blood
2 samples on 2 separate days
Every yr
FIT-DNA
Combines FIT with testing for altered DNA bio markers in CRC cells shed into stool
Single sample
Increased sensitivity but lower specificity —> higher false positive
Every 3 yrs if initial test -ve
Colonoscopy (gold standard)
Lesions can be removed
High sensitivity and specificity
Bowel preparation
Sedation related — invasive procedure
Perforations ; major bleeding
Ideal for high risk indivs
Every 5 to 10 yrs
Flexible sigmoidoscopy (FS)
Examines distal part (descending) colon
No sedation
Lower risk of perforation
Does not need full bowel prep
Only distal polyps or tumours picked up
FS + FIT —> more sensitive than either test alone
Every 5 years
CT colonography
Minimally invasive imaging of entire colon and rectum
Sedation not needed
Detecting adenomas >= 10mm
Full bowel prep and expensive equipment
Less sensitive and cost effective than colonoscopy
Every 5 years
FIT kit
In SG : >= 50 yrs invited to screen for CRC annually
Treatment
Surgery
Radiotherapy —> shrink large tumour before surgery ; kill any residual cancer cells after surgery
Chemotherapy —> cannot be cured by surgery or spread to other parts of body
