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Block D - Digestion and Metabolism > Colorectal Cancer Screening > Flashcards

Colorectal Cancer Screening Flashcards

1
Q

Define surveillance

A

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

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2
Q

Define screening

A

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

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3
Q

Requirements for a good screening test

A

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

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4
Q

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

A 
#3 in 30 - 49
#2 in 50 - 69 and 70+
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5
Q

State of worldwide incidence of CRC

A

Increasing

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6
Q

Incidence of CRC in Canada for men and women

A 
Man = 13.8% (1:13)
Women = 11.6% (1:15)
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7
Q

Number of new cases in Canada per year under 25 yo

A

~25

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8
Q

State of prevalence of CRC and why

A

Increasing because early detection and treatment = more remain alive

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9
Q

State of CRC incidence in North America and why

A

Decreasing due to implementation of population-based screening programs

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10
Q

5 facts about CRC in Quebec (2013)

A

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)

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11
Q

Adenoma to carcinoma sequence

A

Normal –> Proliferative epithelium –> Adenoma –> Carcinoma

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12
Q

What causes the progression of normal epithelium to carcinoma

A

Series of accumulating genetic alterations over years

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13
Q

First gene to be hit by mutations in CRC

A

APC (adenomatous polyposis coli)

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14
Q

2 pathways to CRC

A 
Chromosomal instability
Microsatellite instability (MMR genes)
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15
Q

Most common pathway to CRC

A

Chromosomal instability (75%)

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16
Q

2 characteristics of chromosomal instability pathway to CRC

A

Sporadic (non familial)

Accumulation of genetic defects

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17
Q

4 characteristics of the microsatellite instability pathway to CRC

A

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

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18
Q

3 non-modifiable risk factors for CRC

A

Age
Race
Genetics/heredity

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19
Q

4 modifiable risk factors for CRC

A

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

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20
Q

2 races more predisposed to CRC

A

African-American

Ashkenazi Jewish

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21
Q

3 general diet considerations to prevent CRC

A

Reduce red meat
Increase fruits and vegetables
Increase dietary fibre

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22
Q

3 micronutrients to consider to prevent CRC

A

Calcium
Vitamin D
Folate (reduce??)

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23
Q

5 reasons to reduce red meat intake

A 
Iron
N-nitroso compounds
Polycyclic aromatic hydrocarbons
Heterocyclic amines
Dietary heme
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24
Q

Odd ratio of red meat contributing to CRC

A
  • 1.14 to 1.28

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

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25
Q

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

A

Antioxidants (indoles, carotenes, etc)

26
Q

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

A

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

27
Q

RRR for CRC associated with calcium intake

28
Q

Recommended calcium consumption per day for CRC risk reduction

29
Q

RRR for CRC associated with vitamin D intake

30
Q

Effect of alcohol on CRC risk

A 
High intake (≥2/day) = higher risk of CRC
Consistent across studies --> EPIC trial shows 8% increase over lifetime
31
Q

4 food types that increase risk of CRC

A

Meat
Fat
Refined grain
Dessert

32
Q

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

A

Decreased risk

Decreased risk of recurrence in patients with CRC

33
Q

Drug that decreases risk of polyps and polyp recurrence

A

Aspirin/NSAIDs

34
Q

Risk reduction of aspirin/NSAIDs for polyps as primary prevention

35
Q

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

A

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)

36
Q

Effect of aspirin/NSAIDs as secondary prevention

A

25% reduction in recurrence

37
Q

Recommended dose of aspirin for secondary prevention

A

300 mg/day in post-polypectomy patients

38
Q

Describe obesity’s contribution to CRC risk

A

High BMI (≥30) = 2x risk of CRC

39
Q

Possible reason why women have less risk of CRC than men

40
Q

Effect of exercise on CRC risk

A

10 - 20% decrease

41
Q

Define the fecal occult blood test (FOBT)

A

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

42
Q

Frequency of FOBT

A

Annual (samples collected 3 times over 7 days)

43
Q

Dietary restrictions for successful FOBT

A

No citrus, vitamin C, red meat or NSAIDs

44
Q

Define “occult blood”

A

Small amounts of bleeding not visible to the human eye

45
Q

Problem with FOBT

A

Not very specific and poor compliance

46
Q

Benefit of ROBT

A

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

47
Q

Next step if positive FOBT

A

Full optical colonoscopy

48
Q

Describe the procedure for the fecal immunohistochemistry test (FIT)

A

1) 1 stool sample sent in mail to central lab

2) Lab processes sample with immunohistochemistry to look for blood-antibodies against human heme

49
Q

Benefits of FIT

A

More sensitive than FOBT and probably more user friendly

50
Q

Next step if positive FIT

A

Full optical colonoscopy

51
Q

2 radiologic tests for CRC

A 
Barium enema (double-contrast)
Virtual colonography (3D lumen reconstruction)
52
Q

Next step if radiologic tests are positive

A

Full optical colonoscopy

53
Q

Describe the procedure for barium enema

A

Instillation of contrast and air

54
Q

Problem with barium enema test

A

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

55
Q

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

A

50 - 80% for polyps 1cm

50 - 80% for Stage I/II CRC

56
Q

Describe the procedure for virtual colonography

A

1) Need full mechanical bowel prep and insufflation of air

2) Thin slices with CT scan – digital reconstruction

57
Q

Problem with virtual colonography

A

No sedation and very uncomfortable for patient

Poor detection of polyps under 0.5 cm

58
Q

Polyp detection rates for virtual colonography

A

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

59
Q

2 optical tests for CRC

A

Flexible sigmoidoscopy

Colonoscopy

60
Q

6 screening recommendations for CRC

A

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

61
Q

Gold standard for CRC screening

A

Colonoscopy (every 10 years)

Block D - Digestion and Metabolism (29 decks)

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