Colorectal Cancer Screening Flashcards by Jodeci Malixi

Define surveillance

Active search for cancer in patient with a disease or condition putting them at risk for cancer

How well did you know this?

Not at all

Perfectly

Define screening

Applying a test to a healthy population to confirm the absence of disease (rule it out)

How well did you know this?

Not at all

Perfectly

Requirements for a good screening test

High specificity
High NPV
High sensitivity (for confirmatory tests like colonoscopy)

How well did you know this?

Not at all

Perfectly

In what age groups is colorectal cancer a significant cause of cancer-related deaths?

#3 in 30 - 49
#2 in 50 - 69 and 70+

How well did you know this?

Not at all

Perfectly

State of worldwide incidence of CRC

Increasing

How well did you know this?

Not at all

Perfectly

Incidence of CRC in Canada for men and women

Man = 13.8% (1:13)
Women = 11.6% (1:15)

How well did you know this?

Not at all

Perfectly

Number of new cases in Canada per year under 25 yo

~25

How well did you know this?

Not at all

Perfectly

State of prevalence of CRC and why

Increasing because early detection and treatment = more remain alive

How well did you know this?

Not at all

Perfectly

State of CRC incidence in North America and why

Decreasing due to implementation of population-based screening programs

How well did you know this?

Not at all

Perfectly

5 facts about CRC in Quebec (2013)

6300 new cases (3500 men, 2800 women)
2450 estimated deaths (1300 men, 1500 women)
2nd highest killer in men (after lungs)
3rd highest killer in women (after lung, breast)
2nd highest in Canada (since 8M population)

How well did you know this?

Not at all

Perfectly

Adenoma to carcinoma sequence

Normal –> Proliferative epithelium –> Adenoma –> Carcinoma

How well did you know this?

Not at all

Perfectly

What causes the progression of normal epithelium to carcinoma

Series of accumulating genetic alterations over years

How well did you know this?

Not at all

Perfectly

First gene to be hit by mutations in CRC

APC (adenomatous polyposis coli)

How well did you know this?

Not at all

Perfectly

2 pathways to CRC

Chromosomal instability
Microsatellite instability (MMR genes)

How well did you know this?

Not at all

Perfectly

Most common pathway to CRC

Chromosomal instability (75%)

How well did you know this?

Not at all

Perfectly

2 characteristics of chromosomal instability pathway to CRC

Sporadic (non familial)

Accumulation of genetic defects

How well did you know this?

Not at all

Perfectly

4 characteristics of the microsatellite instability pathway to CRC

Sessile serrated adenomas
Flat, harder to see
Mostly right sided
Often part of genetic syndrome: HNPCC (hereditary non0polyposis colon cancer)

How well did you know this?

Not at all

Perfectly

3 non-modifiable risk factors for CRC

Age
Race
Genetics/heredity

How well did you know this?

Not at all

Perfectly

4 modifiable risk factors for CRC

Diet
Physical activity
Medications
Associated medical conditions (obesity, diabetes)

How well did you know this?

Not at all

Perfectly

2 races more predisposed to CRC

African-American

Ashkenazi Jewish

How well did you know this?

Not at all

Perfectly

3 general diet considerations to prevent CRC

Reduce red meat
Increase fruits and vegetables
Increase dietary fibre

How well did you know this?

Not at all

Perfectly

3 micronutrients to consider to prevent CRC

Calcium
Vitamin D
Folate (reduce??)

How well did you know this?

Not at all

Perfectly

5 reasons to reduce red meat intake

Iron
N-nitroso compounds
Polycyclic aromatic hydrocarbons
Heterocyclic amines
Dietary heme

How well did you know this?

Not at all

Perfectly

Odd ratio of red meat contributing to CRC

1.14 to 1.28

i. e. if you happen to have colon cancer, odds are you ate red meat

How well did you know this?

Not at all

Perfectly

Beneficial component of fruits and vegetables for the reduction of CRC risk

Antioxidants (indoles, carotenes, etc)

What exactly is the benefit shown in studies of fruits&vegetables and dietary fibre in the reduction of CRC risk?

Unclear data RCT for dietary fibre shows no benefit In SOME groups, 35% decrease in adenomas (both food types)

RRR for CRC associated with calcium intake

15 - 30%

Recommended calcium consumption per day for CRC risk reduction

1.2 g

RRR for CRC associated with vitamin D intake

Effect of alcohol on CRC risk

``` High intake (≥2/day) = higher risk of CRC Consistent across studies --> EPIC trial shows 8% increase over lifetime ```

4 food types that increase risk of CRC

Meat Fat Refined grain Dessert

Effect of prudent diet (poultry, fish, fruits and veg) on CRC stats

Decreased risk | Decreased risk of recurrence in patients with CRC

Drug that decreases risk of polyps and polyp recurrence

Aspirin/NSAIDs

Risk reduction of aspirin/NSAIDs for polyps as primary prevention

30 - 40%

Why is aspirin not part of the current recommendations to reduce CRC risk

Individual trials do not support its effect (but pooled cohort study from UK does show 38% decrease in risk over 20 years of follow-up)

Effect of aspirin/NSAIDs as secondary prevention

25% reduction in recurrence

Recommended dose of aspirin for secondary prevention

300 mg/day in post-polypectomy patients

Describe obesity's contribution to CRC risk

High BMI (≥30) = 2x risk of CRC

Possible reason why women have less risk of CRC than men

Estrogen

Effect of exercise on CRC risk

10 - 20% decrease

Define the fecal occult blood test (FOBT)

Screening stools for heme (guaiac-based perocidase test) in 50-74 year olds

Frequency of FOBT

Annual (samples collected 3 times over 7 days)

Dietary restrictions for successful FOBT

No citrus, vitamin C, red meat or NSAIDs

Define "occult blood"

Small amounts of bleeding not visible to the human eye

Problem with FOBT

Not very specific and poor compliance

Benefit of ROBT

RCTs indicate a sustained 15 - 33% CRC mortality reduction Benefit persists for 30 years by indirectly supporting finding the polyp, removing it, and preventing death by preventing adenoma to carcinoma sequence

Next step if positive FOBT

Full optical colonoscopy

Describe the procedure for the fecal immunohistochemistry test (FIT)

1) 1 stool sample sent in mail to central lab | 2) Lab processes sample with immunohistochemistry to look for blood-antibodies against human heme

Benefits of FIT

More sensitive than FOBT and probably more user friendly

Next step if positive FIT

Full optical colonoscopy

2 radiologic tests for CRC

``` Barium enema (double-contrast) Virtual colonography (3D lumen reconstruction) ```

Next step if radiologic tests are positive

Full optical colonoscopy

Describe the procedure for barium enema

Instillation of contrast and air

Problem with barium enema test

Not quite as sensitive as other tests and CRC mortality never directly evaluated

Give the sensitivity of the barium enema test based on polyp size

50 - 80% for polyps 1cm | 50 - 80% for Stage I/II CRC

Describe the procedure for virtual colonography

1) Need full mechanical bowel prep and insufflation of air | 2) Thin slices with CT scan -- digital reconstruction

Problem with virtual colonography

No sedation and very uncomfortable for patient | Poor detection of polyps under 0.5 cm

Polyp detection rates for virtual colonography

< 0.5 cm = poor 0.5 - 1 cm = okay > 1 cm = 90 - 95% detection --> optical scope to remove

2 optical tests for CRC

Flexible sigmoidoscopy | Colonoscopy

6 screening recommendations for CRC

1) High-sensitivty FOBT or FIT annually 2) Flexible sigmoidoscopy ever 5 years + FOBT annually 3) Double-contrast barium enema every 5 years 4) CT colonography every 5 years 5) Colonoscopy every 10 years 6) Fecal DNA testing (no interval specified) NOTE: ALL recommendations begin at age 50

Gold standard for CRC screening

Colonoscopy (every 10 years)