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Alimentary System > Colorectal Cancer > Flashcards

Colorectal Cancer Flashcards

1
Q

what are the risk factors for colorectal cancer?

A

> most are sporadic
10% familial risk
CRC syndromes
inflammatory bowel disease (1%)

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2
Q

what are the risk factors for sporadic cases?

A

> age
male (significant)
previous adenoma/CRC
Environmental influences

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3
Q

what environmental influences affect risk of sporadic cases of colorectal cancer?

A 
> diet: low fibre, low fruit + veg, low calcium, high reed meat, high alcohol
> obesity
> lack of exercise
> smoking
> diabetes mellitus
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4
Q

what are colorectal polyps?

A 
> protuberant growths
> variety of histological types
> epithelial or mesenchymal
> benign or malignant
> can develop into colorectal cancer
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5
Q

are adenomas benign?

A

yes

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6
Q

what tissue does an adenoma originate from?

A

epithelial

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7
Q

what are the 2 main histological types of adenomas?

A

> tubular
villous
(>indeterminate tubulovillous)

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8
Q

what are the different morphological types of adenomas?

A

> pedunculated

> sessile

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9
Q

what factors mean adenoma lesions are high risk?

A

> size
number
degree of dysplasia
villous architecture

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10
Q

what is the molecular sequence that leads to development of a carcinoma from an adenoma?

A

> oncogene activation, k-ras, c-myc
tumour suppressor gene lost (APC, p53, DCC)
defective DNA repair pathway gene (microsatellite instability)

All this leads to cell proliferation and apotosis.

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11
Q

what is the presentation of colorectal cancer?

A

> rectal bleeding
altered bowel opening (diarrhoea)
Iron deficiency anaemia in men and non-menstruating women)
palpable rectal or right lower abdominal mass
acute colonic obstruction (stenosing tumour)
systemic symptoms (weight loss, anorexia)

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12
Q

when are presenting symptoms investigated?

A

> each symptom on its own, investigated if age >60yrs

> combined symptoms, investigated if age > 40 yrs

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13
Q

what sort of colonic malignancy is likely with iron deficiency anaemia?

A

right sided colonic malignancy

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14
Q

why is colonoscopy investigation of choice?

A

tissue biopsies can be taken and therapy can be delivered (polypectomy)

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15
Q

what radiological imaging is available for investigating colorectal cancer?

A

> barium enema
CT colonography
(> CT abdo/pelvis)

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16
Q

what investigations are used for staging colorectal cancer?

A

> CT scan chest/abdomen/pelvis
MRI scan for rectal tumours
PET scan/rectal endoscopic ultrasound in selected cases

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17
Q

describe dukes classification of cancer

A

A: tumour confined to the mucosa
B: tumour extended through mucosa to muscle layer
C: involvement of lymph nodes
D: distal metastatic spread

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18
Q

what treatment may Dukes A or cancer polyps require?

A

endoscopic or local resection

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19
Q

what does the operative procedure depend on?

A

> site
size
stage

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20
Q

can a patient with a single metastasis be operated on?

A

yes if you resect the metastasis as well

21
Q

what is chemotherapy used for in colorectal cancer?

A

> palliation
adjuvant
Dukes c, and b?
to mop up micro metastasis

22
Q

what is used for palliation in advanced disease?

A

chemotherapy and colonic stenting to prevent colonic obstruction

23
Q

what is radiotherapy used for?

A

> rectal cancer only

> as neoadjuvant therapy

24
Q

what is the prognosis for dukes stage a?

A

5 year survival 83%

25
Q

what is the prognosis for dukes stage b?

A

5 year survival 64%

26
Q

what is the prognosis for dukes stage c?

A

5 yr survival 38%

27
Q

what is the prognosis for dukes stage d?

A

5 yr survival 3%

28
Q

what is the aim of population screening?

A

> detect pre-malignant adenomas/early cancers in the general population

29
Q

what are the modalities for population screening in colorectal cancer?

A 
> faecal occult blood test
> faecal immunochemical test
> flexible sigmoidoscopy
> colonoscopy
> ct colonoscopy
30
Q

what is carried out if the FOBT is positive?

A

colonoscopy

31
Q

what age group is screened in the FOBT screening program?

A

50-74 year olds, every 2 years

32
Q

what percentage decrease in the risk of colorectal cancer mortality does the FOBT bring about?

A

a 15% reduction

33
Q

what high risk groups are screened for colorectal cancer?

A

> heritable conditions: FAP, HNPCC
inflammatory bowel disease
familial risk
previous adenomas/ colorectal cancer

34
Q

is FAP dominant or recessive?

A

dominant

35
Q

what are the effects of FAP?

A

> multiple adenomas throughout the colon (50%15yrs, 95% by 35 yrs)
high risk of malignant change in early adulthood, by age 40 if untreated

36
Q

how often are patients with FAP screened?

A

> annually from age 10/12

37
Q

what is usually provided as prophylaxis to patients with FAP at ages 16-25?

A

prophylactic proctocolectomy

38
Q

what extra colonic manifestations can occur with FAP?

A

> benign gastric fundic cystic hyperplastic
duodenal adenomas (in 90% with periampullary cancer)
congenial retinal hypertrophy of pigment epithelia
desmoid tumours

39
Q

what is used in FAP to reduce polyp number and prevent recurrence of high grade adenomas?

A

NSAID chemoprevention

40
Q

is HNPCC an autosomal recessive condition?

A

no it is autosomal dominant

41
Q

what is the mutation in HNPCC?

A

in the DNA mismatch repair genes (MMR)

42
Q

what do tumours in HNPCC typically have?

A

a molecular characteristic called microsatellite instability, frequent mutations in short repeated DNA sequences

43
Q

An early onset right sided colorectal cancer that is associated with other cancers (endometrial, genitourinary, stomach, pancreas) is associated with what condition?

A

HNPCC

44
Q

how do you diagnose HNPCC?

A

clinical criteria (Amsterdam/bathesda and genetic testing

45
Q

how often to patients with HNPCC receive a screening colonoscopy?

A

every 2 years

46
Q

describe screening in patients with a high moderate risk from a family history of CRC

A

5 yearly colonoscopy from age 50 yrs

47
Q

what is surveillance colonoscopy dependent on in IBD?

A

10 years post diagnosis: duration, extent and activity of inflammation and presence of dysplasia

48
Q

patient with previous CRC have a colonoscopy how frequently?

A

every 5 years

49
Q

what does screening in patients with previous adenomas depend on?

A

the number of polyps, size, degree of dysplasia

Alimentary System (33 decks)

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