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#passmed 2022 > Colorectal Cancer > Flashcards

Colorectal Cancer Flashcards

1
Q

What are most colorectal cancers?

A

Adenocarcinomas

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2
Q

Where do colorectal cancers originate from?

A

Epithelial cells lining colon / rectum

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3
Q

What is the pathophysiology sequence of colorectal cancer called?

A

Adenoma-carcinoma sequence

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4
Q

What is the adenoma-carcinoma sequence for colorectal cancer? (3 steps)

A
  1. Normal mucosa
  2. Colonic adenoma (colorectal polyps)
  3. Invasive adenocarcinoma
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5
Q

What are the genetic mutations causing colorectal cancer? (2 things)

A
  1. Adenomatous Polyposis Coli (APC)

2. Hereditary NonPolyposis Colorectal Cancer (HNPCC)

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6
Q

What is the Adenomatous Polyposis Coli (APC) gene responsible for?

What happens when it is mutated?

A

APC gene = tumour suppressor gene

Mutation –> adenomatous tissue growth (e.g FAP aka Familial Adenomatous Polyposis)

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7
Q

What is the Hereditary NonPolyposis Colorectal Cancer (HNPCC) gene responsible for?

What happens when it is mutated?

A

HNPCC gene = DNA mismatch repair gene

Mutation –> DNA repair defects (e.g Lynch syndrome)

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8
Q

What percentage of colorectal cancers are sporadic (develop with no risk factors)?

A

75%

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9
Q

What are the risk factors for colorectal cancer? (7 things)

A
  1. Male
  2. Age
  3. FHx
  4. IBD
  5. Low fibre diet
  6. Smoking
  7. Alcohol
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10
Q

What are the clinical features of LEFT sided colorectal cancers? (4 things)

A
  1. Bleeding / mucus @ PR
  2. Change in bowel habits / obst
  3. Tenesmus
  4. Palpable LIF mass @ PR
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11
Q

What are the clinical features of RIGHT sided colorectal cancers? (4 things)

A
  1. Weight loss
  2. Abd pain
  3. Low Hb
  4. Iron deficiency anaemia symptoms
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12
Q

Why does impeded stool passage happen more in LEFT colon cancer than RIGHT? (3 things)

A
  1. R = stool still liquid (@ ileocecal valve –> asc colon)
  2. R = lumen is larger
  3. L = stool becomes formed here (@transverse colon - desc colon)
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13
Q

What are some differentials that present similarly to colorectal cancer? (2 things)

A
  1. IBD

2. Haemorrhoids

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14
Q

How do you differentiate between IBD and Colorectal cancer? (2 things)

A
  1. IBD = presents younger (20-40 yrs)

2. IBD = diarrhoea w blood + mucus

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15
Q

How do you differentiate between Haemorrhoids and Colorectal cancer?

A

Haemorrhoids = bright red rectal bleeding on stool surface

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16
Q

What lab tests should be done for suspected colorectal cancer? (3 things)

A
  1. FBC (will show microcytic anaemia, iron deficiency anaemia)
  2. LFTs
  3. Clotting
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17
Q

What is the Gold standard imaging for diagnosis of colorectal cancer?

A

Colonoscopy w biopsy

18
Q

What makes a patient unsuitable for a colonscopy? (3 things)

A
  1. Frail
  2. Co-morb
  3. Intolerance
19
Q

What diagnostic imaging should be for suspected colorectal cancer if they are unsuitable for colonoscopy?

A

CT colonography

20
Q

What imaging should be done after diagnosis of colorectal cancer? (3 things)

A
  1. CT chest-abdomen-pelvis
  2. MRI rectum (only rectal cancer)
  3. Endo-anal US (only early rectal cancer)
21
Q

What do you look for in a CT chest-abdomen-pelvis scan in a patient with colorectal cancer? (2 things)

A
  1. Local invasion

2. Distal metastases

22
Q

What are you assessing in a MRI rectum scan in a patient with colorectal cancer? (2 things)

A
  1. Depth of invasion

2. Potential need for pre-op chemo

23
Q

What are you assessing in a Endo-anal US scan in a patient with colorectal cancer?

A

Suitability for trans-anal resection

24
Q

What should a biopsy for colorectal cancer be sent for? (5 things)

A
  1. TNM staging
  2. Histology subtyping
  3. Grading
  4. Assessment of lymphatic / perineural / venous invasion
  5. Check for tumour based markers
25
Q

What is the curative treatment for colorectal cancer?

A

Regional colectomy

+ primary anastamosis (surgical connection between 2 structures) / Stoma formation

26
Q

What colectomy should be done for Caecal / asc colon tumours?

A

R Hemicolectomy

27
Q

What vessels are removed in a R Hemicolectomy? (3 things)

A
  1. Ileocolic vessels
  2. R colic vessels
  3. R branch of M colic vessels

Removed w. their mesenteries

28
Q

What colectomy should be done for Desc colon tumours?

A

L Hemicolectomy

29
Q

What vessels are removed in a L Hemicolectomy? (3 things)

A
  1. L branch of M colic vessels
  2. Inf mesenteric vein
  3. L colic vessels

Removed w. their mesenteries

30
Q

What colectomy should be done for Sigmoid tumours?

A

Sigmoidcolectomy

31
Q

What vessels are removed in a Sigmoidectomy?

A

Inferior mesenteric artery

32
Q

What colectomy should be done for High rectal tumours (5cm + from anus)?

A

Anterior resection

33
Q

What procedure is done to protect anastomosis in an Anterior resection?

A

Defunctioning loop ileostomy

34
Q

Why is an Anterior resection better than an Abdominoperineal (AP) resection?

A

Because Anterior resection leaves rectal sphincter intact if anastomosis is performed

35
Q

What colectomy should be done for Low rectal tumours (less than 5cm from anus)?

A

Abdominoperineal (AP) resection

36
Q

What is excised in an Abdominoperineal (AP) resection? (3 things)

A
  1. Distal colon
  2. Rectum
  3. Sphincters

(Permanent colostomy)

37
Q

How can colorectal cancer presenting with bowel obst be relieved? (2 things)

A
  1. Decompressing colostomy

2. Endoscopic stenting

38
Q

What is the indication for chemotherapy in colorectal cancer?

A

Advanced disease

39
Q

What is the indication for radiotherapy in colorectal cancer?

A

Mainly Rectal cancer

R adiotherapy = R ectal

40
Q

Why is radiotherapy rarely given in colon cancer?

A

Because risk of damage to small bowel

#passmed 2022 (27 decks)

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