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Systems: Alimentary AB > Colorectal Cancer and Screening > Flashcards

Colorectal Cancer and Screening Flashcards

1
Q

What is the epidemiology of CRC?

A
  • 2nd leading cause of cancer death in the Western world
  • 17,000 UK deaths per year
  • 3rd commonest cancer diagnosis overall
  • 2/3rds colonic cancer
  • 1/3 rectal cancer
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2
Q

What are 95% of CRCs?

A

Adenocarcinomas

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3
Q

What are the risk factors for CRC?

A
  • Sporadic cancers
  • Familial risk
  • Inheritable conditions : HNPCC, FAP
  • IBD
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4
Q

What are the risk factors for sporadic CRC?

A
  • Age
  • Male
  • Previous adenoma/CRC
  • Diet
  • Obesity
  • Lack of exercise
  • Smoking
  • Diabetes mellitus
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5
Q

What diet choices can increase your risk of CRC?

A
  • Decreased fire
  • Decreased fruit and veg
  • Decreased calcium
  • Increased red meat
  • Increased alcohol
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6
Q

What do the majority of CRCs arise from?

A

Pre-existing polyps

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7
Q

what are colorectal polyps?

A
  • Protuberant growths that vary in histological types.

- They can be epithelial or mesenchymal and benign or malignant

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8
Q

What is the origin of adenomas?

A

Epithelial

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9
Q

What stage are adenomas?

A
  • Benign

- Pre-malignant

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10
Q

What are the 2 main histological types of adenomas?

A
  • Tubular

- Villous

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11
Q

What is the other histological type of adenoma?

A

Indeterminate tubulovillous

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12
Q

How can adenomas present morphologically?

A
  • Pedunculated

- Sessile

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13
Q

What can affect the severity of an adenoma?

A
  • Size
  • Number
  • Degree of dysplasia
  • Villous architecture
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14
Q

What are the 3 stages involved in the carcinoma sequence?

A
  • Activation of oncogenes
  • Loss of tumour suppressor gene
  • Defective DNA repair pathway genes (microsatellite instability)
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15
Q

What oncogenes are associated with CRC?

A
  • KRAS

- CMYC

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16
Q

What tumour suppressor genes are associated with CRC?

A
  • APC
  • p53
  • DCC
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17
Q

How does CRC present?

A
  • Rectal bleeding
  • Altered bowel opening
  • Iron deficiency anaemia
  • Palpable rectal or right lower abdominal mass
  • Acute colonic obstruction if stenosing tumour
  • Systemic symptoms of malignancy (weight loss, anorexia)
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18
Q

What does presenting with iron deficiency anaemia suggest?

A

Right sided colonic malignancy

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19
Q

When should rectal bleeding and altered bowel opening be investigated?

A
  • Each symptom on its own >60years

- Combined >40 years

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20
Q

What is the investigation of choice in CRC?

A

Colonoscopy

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21
Q

What can also be carried out during colonoscopy?

A
  • Tissue biopsies

- Therapeutic measures (polypectomy)

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22
Q

What is preparation is required for a colonoscopy?

A
  • Sedation

- Bowel preparation

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23
Q

What are the risks when carrying out therapeutic interventions during colonoscopy?

A
  • Perforation

- Bleeding

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24
Q

What radiological imaging can be carried out when investigating CRC?

A
  • Barium enema
  • CT colonography (3D virtual colonoscopy)
  • CT abdo/pelvis
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25
Q

What are the disadvantages of radiological imaging in CRC investigation?

A
  • Ionising radiation
  • Bowel preparation
  • No histology
  • No therapeutic intervention
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26
Q

What can malignant cell invade?

A

Local tissues, metastasise to lymph odes or via blood to other solid organs

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27
Q

What investigations are carried out in the staging process?

A
  • CT scan chest/abdomen/pelvis
  • MRI scan for rectal tumours
  • PET scan / rectal endoscopic ultrasound in selected cases
28
Q

What are the 2 classifications for staging?

A
  • TNM

- Dukes classification

29
Q

What are the stages in the Duke’s classification

A
  • A: tumour confined to mucosa
  • B: tumour extended through mucosa to muscle layer
  • C: involvement of lymph nodes
  • D: distant metastatic spread
30
Q

What is the basis of therapy in CRC?

A

Surgery

31
Q

What does the operative procedure performed depend on?

A
  • Site
  • Size
  • Stage of tumour
32
Q

What are the 2 ways in which surgery can be carried out?

A
  • Laparotomy

- Laparoscopic

33
Q

How are Dukes A and “cancer polyps” treated?

A

Endoscopic or local resection

34
Q

What other procedures can be carried out during surgery for CRC?

A
  • Stoma formation
  • Removal of lymph nodes for histological analysis
  • Partial hepatectomy for metastases
35
Q

When is chemotherapy given as a treatment?

A
  • Adjuvant
  • Dukes C, Dukes B
  • +ve LN histology
  • Mops up metastases
36
Q

What chemotherapy agents are used?

A

5FU (flurouracil) and other agents

37
Q

When is radiotherapy given as a treatment for CRC?

A
  • Rectal cancer only

- Neo-adjuvant +/- chemotherapy to control primary tumour prior to surgery

38
Q

What palliative care can be given for advanced disease?

A
  • Chemotherapy

- Colonic stenting to prevent colonic obstruction

39
Q

How can the outlooks be improved?

A
  • Prevention

- Screening

40
Q

What is the aim of CRC population screening?

A

Detect pre-malignant adenomas and early cancers in the general population

41
Q

What are the modalities of screening?

A

-Faecal occult blood test (FOBT)
-Faecal immunochemical test (FIT)
-Flexible sigmoidoscopy
-Colonoscopy
CT colongraphy

42
Q

Describe the Scottish bowel screening programme.

A
  • Rolled out in 2007
  • Age 50-74 years
  • FOBT every 2 years
  • If FOBT positive then colonoscopy
43
Q

What has the Scottish bowel screening programme resulted in?

A
  • Stage shift in detected cancers

- Reduction in the relative risk of CRC mortality

44
Q

What high risk groups are screened for CRC?

A
  • Heritable conditions (FAP, HNPCC)
  • IBD
  • Familial risk
  • Previous adenomas/CRC
45
Q

FAP

A

Familial adenomatous polyposis

46
Q

HNPCC

A

Hereditary non-polyposis colorectal cancer

47
Q

What type of condition is FAP?

A

Autosomal dominant

48
Q

What occurs in FAP?

A

Multiple adenomas throughout colon

49
Q

What causes FAP?

A

Mutation of the APC gene on chromosome 5

50
Q

What is the risk of malignancy with FAP?

A

High risk of malignancy in early adulthood, in almost all cases by age 40 if untreated

51
Q

What is the screening provided to those with FAP?

A

Annual colonoscopy from age 10-12 years

52
Q

What prophylaxis is offered to those with FAP?

A

Proctocolectomy usually age 16-25

53
Q

What are the extracolonic manifestations of FAP?

A
  • Benign gastric fundic cystic hyperplastic
  • Duodenal adenomas with periampullary cancer
  • Desmoid tumours
  • Congenital retinal hypertrophy of the pigment epithelia (CHRPE)
54
Q

What NSAID chemoprevention is there for FAP?

A

Sulindac reduces polyp number and prevents recurrence of higher grade adenomas in the retained rectal segment

55
Q

What type of condition is HNPCC?

A

Autosomal dominant

56
Q

What causes HNPCC?

A

Mutation in DNA mismatch repair genes

57
Q

What do tumours as a result of HNPCC typically have?

A

A characteristic called microsatellite instability- frequent mutations in short repeated DNA sequences

58
Q

What can HNPCC predispose you to?

A
  • Early onset CRC (40s) right sided

- Associated with cancers at other sites : endometrial, genitourinary, stomach, pancrease

59
Q

How is HNPCC diagnosed?

A
  • Clinical criteria (Amsterdam/Bethesda)

- Genetic testing

60
Q

What is the screening provided to those with HNPCC?

A
  • Screening from age 25

- 2 yearly colonoscopy

61
Q

What screening is provided for those with IBD?

A

Index surveillance colonoscopy 10 years post diagnosis then dependent on duration, extent and activity of inflammation and presence of dysplasia

62
Q

What is the screening provided for previous CRC patients?

A

5 yearly colonoscopy

63
Q

What is the screening dependent on for those with previous adenomas?

A
  • Number of polyps
  • Size
  • Degree of dysplasia
64
Q

What is the screening provided for those with familial history of CRC in the high moderate risk group?

A
  • CRC in 3 FDR none <50 years
  • CRC in 2 FDR mean age <60 years
  • 5 yearly colonoscopy from age 50
65
Q

What is the screening provided to those with familial history of CRC in the low moderate risk group?

A
  • CRC in 2FDR >60 years
  • CRC in 1 FDR <50 years
  • Once only colonoscopy at age 55 years

Systems: Alimentary AB (37 decks)

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