Colorectal carcinoma Flashcards

1
Q

How common is colorectal cancer?

Who does it affect (age/gender)?

A

3rd most common cancer worldwide

2nd most common cause of cancer death in UK

Incidence increases with age ; avg age of diagnosis 60-65yrs

Men>women

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2
Q

What are the risk factors of colorectal cancer?

A
  1. Increasing age
  2. Family hx of colon cancer or colon polyps
  3. Sugar consumption
  4. Colorectal neoplastic polyps
  5. Animal fat (saturated); red meat consumption; low fibre
  6. Chronic IBD
  7. Obesity
  8. Smoking
  9. Alcohol
  10. Previous cancer
  11. Genetic predisposition i.e HNPCC/FAP

*Hereditary non-polyposis colorectal cancer (Lynch syndrome) ; Familial adenomatous polyposis

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3
Q

Which factors reduce the risk of colorectal cancer?

A
  1. Vegetables
  2. Garlic
  3. Milk
  4. Calcium consumption
  5. Exercise (colon only)
  6. Aspirin & other NSAIDs
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4
Q

Normal mucosa => adenoma => invasive cancer

A

How a colorectal cancer progresses

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5
Q

Genetics of colorectal cancer:

Explain chromosomal instability.

A

Chromosomal instability: the most common cause of adenomas in the colon.

Mutation in tumour suppressor genes, initiated by a mutation in gene coding adenomatous polyposis coli (APC).

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6
Q

Genetics of colorectal cancer:

Explain CpG island methylator phenotype (CIMP).

A

CIMP tumours arise via the serrated neoplasia pathway in proximal colon.

Initial mutation in BRAF/KRAS - progress via epigenetic silencing of tumour suppressor and mis-match repair genes by promoting methylation.

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7
Q

Genetics of colorectal cancer:

Explain Micro-satellite instability.

A

Microsatellite instability tumours common in proximal colon.

They arise from defective DNA repair through inactivation of mis-match repair gene.

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8
Q

How does colorectal cancer spread?

A

Colorectal cancer is a polypoid mass with ulceration.

Spreads by direct infiltration through the bowel wall.

Followed by lymphatics, blood, transcoelomic

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9
Q

What are the most common sites of metastases for colorectal cancer?

A

Lungs, liver, bone

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10
Q

Describe the histology of colorectal cancer.

A

Adenocarcinoma with variably differentiated glandular epithelium & mucin production.

Signet rings cells - mucin displaces the nucleus to the side of the cell (uncommon but poor prognosis)

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11
Q

What are the clinical features of right-sided and left-sided colorectal cancer?

A
Left-sided colon: 
Bleeding/mucus PR 
Altered bowel habit or obstruction
Looser, more frequent stool
Tenesmus (need to empty bowels, with little to no stool passed)
Rectal mass
Right-sided colon:
Weight loss
Low Hb (symptoms of anaemia: fatigue, lethargy etc)
Abdominal pain
Obstruction less likely
Either:
Abdominal mass
Perforation
Haemorrhage 
Fistula

Cancers arising in caecum or right colon often asymptomatic until they present with iron deficiency anaemia.

Cancer may present with bowel obstruction

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12
Q

How do you examine the patient?

A

Digital exam and GI exam

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13
Q

What are the diagnostic investigations for colorectal cancer?

A

Gold standard: colonoscopy + biopsy for histology

Double contrast barium enema - visualise the large bowel (now superseded by CT)

CT - chest, abdo and pelvic. Tumour size, local spread, liver & lung metastases for tumour staging

PET scan - occult metastases + for suspicious lesions on CT or MRI

Endoanal ultrasound & pelvic MRI - staging rectal cancer

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14
Q

What is the management for colorectal cancer?

A

Long-term survival = cancer completely cleared by surgery with adequate clearance margins and regional lymph node clearance.

Usually laparoscopic surgery.

Right hemicolectomy: caecal, ascending and proximal transverse colon tumours

Left hemicolectomy: distal transverse, descending tumours

Sigmoid colectomy for sigmoid tumours

Anterior resection: low sigmoid or high rectal tumours

Abdomino-perineal resection: low rectal tumours(<8cm from anus) => permanent colostomy and removal of rectum & anus

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15
Q

What is total mesorectal excision (TME) used for?

A

Rectal cancers where it removes the entire mesorectal tissue surrounding the cancer.

TME + radiotherapy reduces rates of local recurrences of rectal cancer

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16
Q

What technique is used for cancers anywhere in the colon (apart from rectum)?

A

Segmental resection and restorative anastomosis, with removal of the draining lymph nodes as far as the root of the mesentery.

17
Q

What is local transanal endoscopic surgery used for?

A

Superficial localised rectal cancers

18
Q

Why is radiotherapy not useful in in colonic cancers proximal to the rectum?

A

Difficulties delivering sufficient dose to the tumour without being toxic to nearby healthy tissue

19
Q

Which screening tools are available for colorectal cancer?

A

UK National bowel cancer screening program (>55years):

  1. FOB (faecal occult blood test) or FIT (faecal immunochemical test) => FOB is less sensitive therefore is not used as commonly as FIT
  2. Flexible sigmoidoscopy
  3. GOLD STANDARD : Colonoscopy
20
Q

What are the investigations carried out for suspected colorectal cancer?

A
FBC (microcytic anaemia)
FOB test 
Flexible sigmoidoscopy or colonoscopy
LFT
Liver MRI/US
21
Q

Which staging method is used for colorectal cancer?

A

TNM now preferred to Duke’s staging criteria

22
Q

What is Hartmann’s procedure?

A

Surgical resection of the recto-sigmoid colon, closure of the anorectal stump and formation of an end colostomy.

Used in emergency bowel obstruction, perforation, palliation

23
Q

What is the prognosis of colorectal cancers?

A

Depends on age and stage - stage 1 of disease 5yr survival is ~75% but stage 4 is 5% survival