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M104 T1 > M104 T1 L13 > Flashcards

M104 T1 L13 Flashcards

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1
Q

What is the third most common cancer in women after breast and lung cancer?

A

bowel cancer

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2
Q

How common is bowel cancer in men?

A

it is the third most common cancer in men after prostate and lung cancer

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3
Q

What is the global incidence of bowel cancer?

A

High incidence in the western world; low incidence in Asia and Central Africa

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4
Q

How does bowel cancer affect men and women ratio-wise?

A

affects both equally

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5
Q

What type of disease is bowel cancer?

A

it is believed to be an environmental disease and potentially preventable

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6
Q

What is a migrational risk factor of bowel cancer?

A

Individuals who migrate from a low risk area to a high risk area increase their risk of developing bowel cancer
e.g. Japanese who migrated to the USA acquired the risk of their host country

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7
Q

What are the risk factors of bowel cancer in Western countries?

A

Foods rich in red meat & fat increase the risk of
bowel cancer
Food rich in vegetables, fruit & fibre reduces the risk
of bowel cancer by ↑ faecal bulk & reduces transit
time
Physical activity & low BMI are associated with low
risk of bowel cancer

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8
Q

What are the migrational risk factors of bowel cancer?

A

Migration
Longstanding UC
Crohn’s disease; to a lesser extend than UC
Presence of adenoma in the large bowel
Previous history of bowel cancer surgery
Family history of bowel cancer
Old age – older people are also at risk of cancer in other organs besides bowel cancer

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9
Q

What reduces the risk of bowel cancer?

A

Diet rich in high fibre, fruit & vegies

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10
Q

How does high fibre diet reduce bowel cancer?

A

By increasing the formation of short chain FAs which promote healthy gut micro-organisms and reduces the proliferation of potentially neoplastic cells
Increasing stool bulk reduces transit time and potential carcinogens in the stool have a shorter contact with the bowel mucosa
it reduces formation of secondary bile acids which are potentially carcinogenic

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11
Q

What material are most polyps in the large bowel made up of?

A

dysplastic epithelium

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12
Q

What does dysplasia literally mean in Greek?

A

dys = bad; plasis = formation

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13
Q

What is the difference between the cells that make up polyps in the large bowel and between cancerous cells?

A

the cells have morphological features of cancer but without invasion of the surrounding tissue

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14
Q

What is the difference between low and high grade dysplasia?

A

Low – early precancerous features

High - advanced precancerous features with high risk of invasion if not removed

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15
Q

How is a polyp found to be cancerous or not?

A

microscopic examination by the pathologist

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16
Q

What are the three types of polyps in bowel cancer screening?

A

benign (innocent, hyperplastic)
pre-cancerous (adenoma, dysplastic)
cancerous - if the cancer is polypoid, do not use the term polyp

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17
Q

What is the difference between the appearance of tubular and villous adenomas?

A

Tubular - has test tube-like appearance

Villous - has finger-like appearance

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18
Q

What are features of benign polyps?

A

consist of numerous goblet cells compared to normal mucosa

has a lace-like pattern

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19
Q

What is a feature of Tubulovillous adenoma?

A

has a mixture of tubular and villous features

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20
Q

What are the morphological features of the Adenoma-Carcinoma Sequence?

A

macroscopic and histological features being mirrored at genetic level where there are stepwise genetic alterations

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21
Q

What driver mutations are involved in the Adenoma-Carcinoma Sequence?

A

APC, KRAS, SMAD4, and TP53 genes

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22
Q

What is the evidence for the Adenoma - Carcinoma Sequence?

A
  • Populations with high adenoma prevalence also have a high cancer prevalence
  • the distribution of adenomas in the large bowel mirrors that of bowel cancer
  • the peak incidence of polyps pre-dates the development of cancer
  • Residual adenoma is found in most cases of early invasive cancer
  • the risk of cancer is directly related to the number of polyps
  • Programmes which follow-up patients and remove adenomas reduce the incidence of bowel cancer
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23
Q

What does the ACS state?

A

that most sporadic cancers which are not genetically determined arise from adenomas

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24
Q

What evidence is there that the distribution of adenomas in the large bowel mirrors that of bowel cancer?

A

60% of the cancer arise in the left colon and rectum most adenomas arise in this region

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25
How is bowel cancer screening conducted?
using flexible sigmoidoscopy
26
What is an example of how the peak incidence of polyps pre-dates the development of cancer?
the peak age for adenomas is around 60 years | the median age for bowel cancer is 71 years
27
What is an example of how the risk of cancer is directly related to the number of polyps?
patients with Familial Adenomatous Polyposis have high risk of cancer
28
What is the criteria to make a diagnosis of FAP?
having a minimum of 100 polyps
29
How many polyps are usually in patients with FAP?
500 – 2500 in the large bowel
30
What is the link between FAP and cancer?
there is a 100% risk of development of cancer by age of 30
31
What happens to FAP patients around the age of 20?
they undergo a prophylactic colectomy
32
What percentage of bowel cancer cases are developed from FAP?
1%
33
What type of condition is FAP genetically? (HAD)
Hereditary autosomal dominant
34
What is the defective gene responsible for FAP, and on what CMS is it located?
the APC gene on CMS 5q21
35
What type of protein is Adenomatous Polyposis Coli?
a tumour suppressor
36
When do FAP patients acquire the first abnormal caustative gene?
when in utero as a germ cell
37
How do FAP patients develop polyps?
when they acquire the second genetic abnormality in the somatic cells - the ‘second hit’ none at birth
38
What is the effect of the second hit in FAP?
it paves the way for the development of polyps from a young age and throughout the teen years
39
What is the Two Hit Hypothesis in Hereditary Bowel Cancer?
when, in FAP, the patient is born with a single genetic abnormality (first hit) and acquires the second genetic abnormality (second hit) after birth to develop adenomas then cancer
40
What is the Two Hit Hypothesis in Sporadic Bowel Cancer?
the person acquires the two hits in somatic cells to develop adenomas then cancer
41
Who proposed the two hit hypothesis and why?
Knudson, to explain hereditary retinoblastoma
42
What is the most common primary malignant intraocular cancer in children?
retinoblastoma
43
What is the effect of the Second Hit in FAP patients?
the loss of the second set of normal genetic material during the ‘second hit’ leads to loss of heterozyosity cells will acquire two identical copies of abnormal genes i.e. become homozygous for the cancer gene after the second hit the cells acquire more genetic abnormalities to progress with adenoma-carcinoma sequence
44
What is the effect of the first hit in FAP patients?
it is important in the initiation of bowel cancer | With one copy of abnormal gene, the cells are heterozygous
45
What happens in the Fearon & Vogelstein model?
genetic abnormalities are acquired in a stepwise fashion which result in the progression from normal mucosa to adenoma to cancer
46
What genetic abnormalities are associated with bowel cancer?
``` Lynch Syndrome (Attenuated) FAP, MAP Familial Colorectal Cancer Type X Serrated Polyposis Syndrome Hamartomatous Polyposis Syndrome ```
47
What did Lynch Syndrome used to be known as?
Hereditary Non-polyposis Colorectal Cancer
48
What is the criteria for Attenuated FAP?
less than 100 adenomas
49
What cancers is lynch syndrome associated with? (SUE)
small bowel
50
What area of the body does lynch syndrome predominantly affect?
the caecum and right colon
51
What age group does lynch syndrome affect?
under 50s
52
What percentage of bowel cancer cases are caused by Lynch Syndrome?
2-3%
53
Are there any precursor polyps in Lynch syndrome?
no
54
What conditions are routinely tested for Lynch Syndrome genetic mutations?
Bowel cancer from young patients and advanced cancers | whether they have a family history of cancer or not
55
What are the genetics of Lynch Syndrome compared to FAP?
Very different but, similar to FAP individuals, LS patients inherit the defective copy of the mismatch repair gene in utero (first hit) and acquire the second copy during life (second hit) and develop cancer
56
What are the genetics of Lynch Syndrome compared to FAP?
During replication the DNA base pairs can mismatch e.g. Guanine – Thymine instead of GC There are mismatch repair genes which act as ‘spell checkers’ and correct these mismatches Without the repairs the errors accumulate and create microsatellites, which are fixed for life this leads to expansion and contractions of these repeat nucleotides causing microsatellite instability
57
What are microsatellites otherwise known as?
short tandem repeats
58
What are the mismatch repair genes involved in Lynch Syndrome?
MSH2 (2p16) and MLH1 (3p21) genes - 30% of LS | PMS1 and PMS2
59
What does microsatellite instability indicate in Lynch Syndrome?
defective mismatch repair
60
What genes are routinely tested for in bowel cancer?
the mismatch repair genes involved in Lynch Syndrome
61
What criteria is used to assess Lynch syndrome?
the Amsterdam Criteria
62
What are the features of the Amsterdam Criteria?
Three or more relatives with LS-associated cancer - One affected patient should be a first-degree relative of the other two - Two or more successive generations should be affected - Cancer in one or more affected relatives should be diagnosed before the age of 50 years; - FAP should be excluded in any cases of colorectal cancer - Tumours should be verified by pathological examination
63
What are examples of LS-associated cancer?
``` bowel cancer cancer of the endometrium small bowel ureter renal pelvis ```
64
What are the symptoms of bowel cancer?
Can be asymptomatic and detected during screening Change in bowel habit - constipation alternating with diarrhoea due an obstructive cancer Bleeding from the rectum Anaemia especially with cancers of the caecum due to slow occult blood loss Abdominal pain due to obstruction
65
How is bowel cancer diagnosed?
History and clinical examination Flexible sigmoidoscopy and colonoscopy with biopsy and histological examination CT Colonography for patients who cannot tolerate colonoscopy Staging CT scan for distal metastasis MRI for rectal cancer to assess local spread
66
What is the pathology of bowel cancer?
Histologically adenocarcinoma | Graded as well, moderate & poorly differentiated
67
What is meant by the three grades of adenocarcinomas in bowel cancer?
Well differentiated - resembles normal colonic mucosa Moderately differentiated (most common) Poorly differentiated - minimal or no glandular differentiation
68
What are the four main stages of tumour size in bowel cancer?
``` T1 = Invasion of the submucosa; the muscularis propria is clear T2= Involves of the muscularis propria without full thickness invasion – in this case there is invasion of the inner layer and not the external layer T3 = Invasion of the full thickness of the bowel wall but not the serosa T4 = the cancer has gone through the bowel wall and is present on the serosa ```
69
What are the extra two stages of tumour size in bowel cancer?
T3 N1 - cancer which has invaded the full thickness of the bowel with lymph node metastasis M1 - liver metastasis from bowel cancer
70
How can bowel screening help to prevent cancer?
by detecting polyps before they turn into cancer | it will detect early cancers at a curable stage
71
What methods can be used to screen for bowel cancer?
Stool test / FIT | Flexible sigmoidoscopy, Colonoscopy (ideal)
72
Why are colonoscopies not performed in the UK despite being ideal?
it requires sedation and expertise | it is associated with 1 - 2% risk of perforation
73
In what country is colonoscopy used for screening?
in the usa
74
What methods are used to screen for bowel cancer in the UK?
flexible sigmoidoscopy at 55years | FIT from 60-74 year olds every two years
75
What are the features of sigmoidoscopies when being used to screen for bowel cancer?
they detect polyps and cancers in the rectum and left colon
76
What is the purpose of FIT?
to test for occult blood - hidden blood in the stool, not visible to the naked eye Positive test does not mean one has bowel cancer Haemorrhoids & inflammation can cause a positive test
77
How does FIT work to test for stool?
using an ATBY-antigen reaction | the reagent contains an ATBY specific to human blood
78
How are FITs carried out?
The participants receive a stool kit The test is done in the privacy of their own home The stool kit is send to the lab The resultant antigen-antibody reaction is read by machine
79
What might cause occult bleeding?
Ulcerating cancers | Trauma to large polyps due to friction with stool
80
What happens after a positive stool test?
colonoscopy referral
81
What do colonoscopies detect in patients who have had a positive FIT?
polyps (benign and precancerous) | early and advanced cancers
82
What do colonoscopies NOT detect in patients who have had a positive FIT?
non-bleeding polyps / cancers
83
How often are FITs repeated for patients who test negative?
every two years

M104 T1 (15 decks)

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