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6. Cancer > colorectal cancer > Flashcards

colorectal cancer Flashcards

1
Q

What are colorectal cancers?

A

Most colorectal cancers are adenocarcinomas that evolve from polyps, which may be present for ten years or more before malignancy develops. Colorectal cancer is locally invasive but metastatic spread may be evident before local growth produces symptoms. The most common site for metastatic spread is the liver. Other sites (eg, the lungs, brain and bone) are unusual in the absence of liver metastases.

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2
Q

What age group experiences the most colorectal cancers?

A

85-89

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3
Q

What is the most common site for colorectal cancer?

A

Rectum

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4
Q

What are the risk factors for colorectal cancers?

A
  1. Family history
  2. Inflammatory bowel disease
  3. Polyposis syndromes
  4. Diet rich in meat, low in fibre
  5. Alcohol, obesity, smoking
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5
Q

What family history puts you at risk of developing colorectal cancer?

A

Lynch syndrome
Gardner syndrome
Familial adenomatous polyposis

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6
Q

What cells does colorectal cancer originate from?

A

Epithelial cells

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7
Q

What is the pathogenesis of colorectal cancer?

A

Mutation in Wnt signalling pathway inntestinal crypt stem cells

Mutation in APC and KRAS genes

P53 mutation

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8
Q

At what age does colorectal cancer screening start?

A

60, this is realistically too late

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9
Q

What is the adenoma-carcinoma sequence?

A

Normal → hyperproliferation → micro-adenoma → small/intermediate/large adenomous polyp → cancer

Takes 10-15 years to develop

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10
Q

What are the mutation in Lynch that are associated with colorectal cancer?

A

MLH1
MSH2
MSH6
PMS2

Makes for absence of mismatch repair system in nucleus

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11
Q

What is a key characteristic in Lynch syndrome?

A

DNA mismatch repair which causes microsatellite instability

Used as a screening tool for mismatch repair defects in DNA

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12
Q

How is Lynch syndrome inherited?

A

Autosomal dominant

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13
Q

What are the Amsterdam criteria in Lynch syndrome?

A

3-2-1 rule for diagnosing Lynch

3 relatives with bowel cancer in 2 generations, 1 is a first degree relative and 1 had cancer by the age of 50

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14
Q

What is the clinical history of Lynch syndrome?

A
  1. Family history
  2. Onset < 45 years
  3. Proximal cancers
  4. Multiple synchronous primary cancers
  5. Mucinous, poorly differentiated lymphocyte infiltration and singlet ring formation
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15
Q

What are symptoms of right colon cancers?

A

Weight loss, silent colon, anaemia, occult bleeding, mass in right iliac fossa, disease more likely to be advanced at presentation

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16
Q

What are symptoms of left colon cancers?

A

Colicky pain, rectal bleeding, bowel obstruction, tenesmus, mass in left iliac fossa, early change in bowel habit, less advanced disease at presentation.

17
Q

What are the most common presenting complaints for colorectal cancer?

A

Rectal bleeding
Persistent change in bowel habit
Anaemia

18
Q

In colorectal cancer, what do jaundice and hepatomegaly present?

A

Advanced disease and liver metastases

19
Q

When would you do faecal immunochemical testing?

A

Adults without rectal bleeding who:

  1. Are aged 50 or over with unexplained abdominal pain or weight loss; or
  2. Are aged under 60 with changes in their bowel habit or with iron-deficiency anaemia; or
  3. Are aged 60 and over and have anaemia even in the absence of iron deficiency.
20
Q

What investigations would you do for suspected colorectal cancer?

A
  1. FBC + LFT (anaemia, alkaline phosphatase raised in liver metastases)
  2. Colonoscopy with biopsy
  3. eGFR to know whether you can use contrast
  4. CT scan
21
Q

When would you refer someone for suspected colorectal cancer?

A
  1. Aged 40 years and over with unexplained weight loss and abdominal pain; or
  2. Aged 50 and over with unexplained rectal bleeding; or
  3. Aged 60 and over with anaemia or changes in bowel habit
22
Q

What would you use to stage colorectal cancer?

A

Contrast-enhanced CT and Dukes’ staging classification

23
Q

What are the stages of Dukes’ staging classification?

A

Dukes’ A - the cancer is only in the innermost lining of the bowel or slightly growing into the muscle layer.
Dukes’ B - the cancer has grown through the muscle layer of the bowel.
Dukes’ C - the cancer has spread to at least one lymph node close to the bowel.
Dukes’ D - the cancer has metastasised to other areas - eg, the liver, lungs or bones.

24
Q

How would you manage colorectal cancer?

A

Surgery
1. Right hemicolectomy: for tumours in the caecum, ascending and proximal transverse colon.
2. Left hemicolectomy: if in the distal transverse colon or descending colon.
3. Sigmoid colectomy: for tumours of the sigmoid colon.
Anterior resection: if in the low sigmoid or high rectum. Anastomosis is achieved at the first operation.

Radiofrequency ablation for liver metastases

25
Q

What is the most common site for colorectal cancer to metastasise to?

A

Liver

Over 50% of patients with colorectal cancer will develop liver metastases

Liver resection, with neoadjuvant and adjuvant chemotherapy, is the optimal treatment for colorectal metastases

26
Q

What is the prognosis for colorectal cancer?

A

Around half of people diagnosed with colorectal cancer survive for at least five years after diagnosis

27
Q

What is the screening method for colorectal cancer?

A

Fecal occult blood testing (FOBT)

28
Q

A 75 year old man receiving palliative care for metastatic bowel cancer is semiconscious and being given diamorphine hydrochloride and haloperidol via a syringe driver. His breathing is becoming increasingly noisy. His family are finding this distressing.

Which is the most appropriate drug management?

A) Amoxicillin
B) Furosemide
C) Hyoscine
D) Levomepromazine
E) Midazolam
A

C - Hyoscine, specifically hyoscine butylbromide not hyoscine hydrobromide as this crosses the blood brain barrier causing excessive sedation. As an anticholinergic hyoscine reduces chest secretions. It’s also used as an antiemetic for travel sickness.

29
Q

What is Familial adenomatous polyposis?

A

An inherited condition in which numerous adenomatous polyps form mainly in the epithelium of the large intestine

30
Q

What inherency pattern does Familial adenomatous polyposis follow?

A

Autosomal dominant

31
Q

What does Familial adenomatous polyposis lead to?

A

Colorectal cancer, often before the age of 35

32
Q

What is raised alkaline phosphatase a sign of?

A

Liver metastasis

33
Q

If a patient is MSI status positive, what therapy can you use?

A

Immune checkpoint therapy

34
Q

Where is KRAS located?

A

Chromosome 12

35
Q

What cancers are commonly associated with KRAS mutations?

A

Lung
Colorectal
Pancreatic

36
Q

What treatment can you use for specific KRAS mutated cancers?

A

anti-EGFR monoclonal antibodies (Cetuximab and panitumumab)

6. Cancer (15 decks)

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