Colorectal Cancer Prevention and Screening
Primary Prevention

NHMRC Recommendations (Evidence-based):

1. Moderate physical activity 30-60 min / day
2. Weight in healthy BMI range.
3. Avoid smoking
4. Limit alcohol to 2/day
5. Reduce energy intake to <2500 calories / day (<2000 in women)
6. Reduce dietary fats to <25% of intake
7. Limit red meat to moderate intakes of lean meat
8. 5+ serves per day of vegetables and 2 for fruit
9. Poorly soluble fibres (e.g. wheat bran).
10. Adequate calcium intake
11. Aspirin reduces risk of polyps in those who have had an adenoma removed.


Justification for Screening
Second most deadly cancer
Early pickup of polyps can prevent development of cancer.
Guidelines

American Cancer Society

Principles
Divide population into:
- average risk = 75%
- moderate risk = 20%
- high risk = 5%

Average risk
Screen at 50 yrs
- annual PR exam
- fecal occult blood tests yearly
- flexible sigmoidoscopy every 5 yrs
- OR colonoscopy / double contrast enema every 5-10 yrs

Moderate risk
1 or more 1st degree relatives
OR personal history of neoplasia
Screen at 40y, or 10y earlier than youngest affected relative's age at diagnosis
- colonoscopy every 5 years.
If pt has personal history of a significant adenomatous polyp (>1cm):
- colonoscopy annually until negative, then 5-yearly.

High risk
Hereditary or genetic predisposition
Like HNPCC or FAP, IBD >10y
Screen annually
Genetic counselling for family.
Surgical referral if prophylactic colectomy recommended as per condition.

NHMRC Guidelines
Essentially the same as the above.

Average Risk
1. FOB testing for all Australians over 50 years, at least once every two years (strongly recommended)
2. Flexible sigmoidoscopy every 5y from aged 50 (equivocal)

Category 1 Risk
- one first degree relative with colorectal Ca diagnosed at age 55 or over.
--> RR 2x
1. FOB testing every second year
2. Flexible sigmoidoscopy (or colonoscopy) every 5 years from aged 50.

Category 2 Risk
- one first degree relative with colorectal Ca, diagnosed <55 yrs
--> RR 3-6x
Colonoscopy every 5 years, starting age 50, or 10y younger than first diagnosis of bowel Ca in family.
If can't get a colo, then sigmoidoscopy and double-contrast Ba enema
Full family hx and update regularly for HNPCC possibility.
- routine genetic testing not currently appropriate.
- if Bethesda criteria met, Tumour testing for HNPCC-related changes (immunohistochm and microsatellite instability)

Category 3 Risk
- two first degree relatives diagnosed at any age
--> RR 3-6x
Specialist genetic testing after counselling --> see below if dx +ve
Else as for Category 2 risk.
Role of NSAIDs in prevention is unclear

FAP
If negative on genetics then obviously at average risk.  Else:
1. Total colectomy and ileorectal anastomosis or restorative proctocolectomy recommended when ready for surgery
2. Surveillance should begin by age 12-15y, except in attenuated FAP (then guided by colonoscopy)
3. Duodenal surveillance from age 25+

HNPCC
1. Annually or two yearly colonoscopy from age 25+
- or 5y before age at first cancer.
2. Surveillance for uterus and ovarian cancer at age 30-35, or 5y earlier than youngest affected relative.
3. Use Revised Bethesda Guidelines for selection of cancers for MSI testing and staining

Follow-up of Polyps
1. 1 year if tumour resected
2. 3 years if large adenomas or high grade dysplasia, or villous adenoma, or 3+ adenomas, or aged 60+ with first degree relative
3. Else 5 years is fine.
See also more complete plan here