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MBChB - Y2 - Systems - Gastrointestinal > Colorectal Cancer and Screening > Flashcards

Colorectal Cancer and Screening Flashcards

1
Q

What type of cancer is colorectal cancer most commonly?

A
  • 95% adenocarcinomas
  • 2 thirds colonic, 1 third rectal
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2
Q

What are the comon ways colorectal cancer arises?

A
  • Most (85%) are sporadic with no familial/genetic influence
  • 10% have a familial risk
  • Inheritable conditions: HNPCC (5%), FAP (<1%), other CRC syndromes
  • 1% associated with underlying Inflammatory Bowel Disease (IBD)
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3
Q

What are risk factors for sporadic cases of colorectal cancer?

A

Age

Male gender

Previous adenoma/CRC

Environmental influences:

–Diet (reduced fibre, reduced fruit & veg,

reduced calcium, increased ­red meat, increased ­alcohol,)

–Obesity

–Lack of exercise

–Smoking

–Diabetes Mellitus

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4
Q

What do the majortiy of colorectal cancers arise from?

A

Existing polyps

  • protuberant growths
  • variety of histological types
  • epithelial or mesenchymal
  • benign or malignant
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5
Q

What is the origin of adenomas?

A

Epithelial origin

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6
Q

What are the two histological types of adeomas?

A

•2 main histological types – tubular (75%), villous (10%), indeterminate tubulovillous (15%)

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7
Q

What are the oncogenes responsible for carcinoma of the colon?

A

k-ras, c-myc

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8
Q

What are the tumour suppressor genes that are lost in the process of carcinoma formaiton?

A

– APC, p53, DCC

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9
Q

What is the presentation of colorectal cancer?

A

Rectal bleeding

Altered bowel opening - diarrhoea

Iron deficiency anaemia

Iron Deficiency Anaemia men of any age and non-menstruating women (more likely to have right sided colonic malignancy)

Palpable rectal or right lower abdominal mass

Acute colonic obstruction if stenosing tumour

Systemic symptoms of malignancy: Weight loss, Anorexia

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10
Q

How do alarm features come in play when diagnosing colorectal cancer?

A

Poor sensitivity and specificity for diagnosis of colorectal cancer

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11
Q

What are the investigations for colorectal cancer?

A

Colonoscopy

Radiological imaging: barium enema, CT colonography, CT of abdomen and pelvis

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12
Q

What are benefits of colonoscopy?

A

Allows tissue biopsies to be taken

Can be used therapeutically (polypectomy)

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13
Q

What are the risks associated with colonoscopy?

A

Perforation

Bleeding

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14
Q

What are the disadvantages of radiological imaging?

A

Ionising radiation

No histology

No therapeutic intervention

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15
Q

What are the staging investigations for 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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16
Q

What is the TNM staging for colorectal cancer?

A

T1-T4 local disease progression

N0 – N1 lymph nodes involvement

M0 – M1 distant metastases

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17
Q

What is the Duke’s classification for colorectal cancer staging?

A

A – Tumour confined to mucosa

B – Tumour extended through mucosa to muscle layer

C – Involvement of lymph nodes

D - Distant metastatic spread

18
Q

What is the treatment for colorectal cancer?

A

Surgery in 80% of cases

Dukes A and ‘cancer polyps’: endoscopic or local resection

19
Q

What else might be removed during a colestomy?

A

Lymph nodes for histological analysis

Partial hepatectomy for metastases

20
Q

What is involved in palliative care of colorectal cancer?

A

Chemotherapy, colonic stenting to prevent colonic obstruction

21
Q

When is chemotherapy administered?

A

Advanced disease

Used as an adjuvant - to suppress secondary tumour formation

Used in cases of Dukes C and Dukes B

Used in positive cases of lymph node involvement

22
Q

When is radiotherapy indicated?

A

Rectal cancer only

‘neoadjuvant’ +/- chemotharapy to control primary tumour prior to surgery

23
Q
A
24
Q

What are prevention measures against getting colorectal cancer?

A

30 minutes of physical activity most days

Maintain healthy BMI (18.5 - 25)

Eat 5 or more portions of fruit or veg a day

Not to smoke

25
Q

What are modalities of colorectal cancer population screening?

A

–Faecal occult blood test (FOBT)

–Faecal immunochemical test (FIT)

–Flexible Sigmoidoscopy

–Colonoscopy

–CT Colonography

26
Q

What are the features of the scottish bowel screening programme 2007?

A

Roll out in 2007

Age 50-74 years

FOBT every 2 years

If FOBT positive ® colonoscopy

Stage shift in detected cancers (48% Dukes A v 11% in non-screened)

~15%reduction in the relative risk of colorectal cancer mortality

27
Q

Who might require different screening programme? (who is contained within the ‘high risk’ group)

A

Heritable conditions

–FAP (familial adenomatous polyposis)

–HNPCC (hereditary non-polyposis colorectal cancer)

Inflammatory bowel disease

Familial risk

Previous adenomas/Colorectal cancer

28
Q

What type of condition is FAP and what is it caused by?

A

Autosomal dominant condition

Caused by mutation of the APC gene on chromosome 5 (25 % are due to new mutations)

29
Q

What is the main risk attaced to FAP?

A

High risk of malignant change in early adulthood, in almost all cases by age 40 yrs if untreated

30
Q

What is management of FAP?

A

Screening – annual colonoscopy from age 10-12 yrs

Prophylactic proctocolectomy usually age 16 - 25 yrs

31
Q

What type of condition is HNPCC and what causes it?

A

Autosomal dominant condition, caused by the mutation in a DNA mismatch repair gene.

(MLH1 and MSH2)

32
Q

What is typical about the tumours in HNPCC?

A

They have a molecular characteristic called microsatellite instability

Frequent mutations in short repeated sequences of DNA (microsatellites)

33
Q

What type of cancer is assocaited with HNPCC?

A

Early onset colorectal cancer (40’s) right sidedn

Associated with cancers at other sites – endometrial, genitourinary, stomach, pancreas

34
Q

What is the screening programme for HNPCC?

A

Screeening from age 25 every 2 years

35
Q

What is the diagnostic test for HNPCC?

A

Amsterdame / bethesda cliical criteria or genetic testing

36
Q

For those with a familial history of CRC, who is at a ‘high moderate risk’?

A

CRC in 3 first degree relatives who are all over 50

or

CRC in 2 first degree relatives who have a mean age of less than 60

37
Q

What is the screening for high moderate risk patients as a result of familial history?

A

5 year colonoscopy from the age of 50

38
Q

For those with a familial history of CRC, who is at a ‘low moderate risk’?

A

CRC in 2 first degree relatives who are 60 or over

OR

CRC in one first degree relative who is over 60

39
Q

What is the screening for lowmoderate risk patients as a result of familial history?

A

–once-only colonoscopy at age 55 yrs

40
Q
A

MBChB - Y2 - Systems - Gastrointestinal (38 decks)

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