Colorectal Carcinoma Flashcards
Define colorectal carcinoma.
Malignant adenocarcinoma of the large bowel
What is the aetiology of colorectal cancer?
Mix of genetic and environmental factors.
Genetic (2-5%): most common family syndromes associated with single gene defects:
- Familial adenomatous polyposis (FAP)
- Lynch syndrome (HNPCC)
Environmental:
- Obesity
- Low dietary fibre intake
- High intake of red and processed meat
What is the epidemiology of colorectal carcinoma?
- 2nd most common cause of cancer-related death and 3rd most common cancer in West
- Average age at diagnosis is 60-65 years
Where are most colorectal carcinomas located?
- 60% = rectum and sigmoid colon
- 15-20% = ascending colon
Remainder in transverse and descending colon
Describe the Dukes’ classification of colorectal carcinoma.
Dukes’ classification for STAGING (spread) and 5 year survival %
A: Limited to the bowel wall - 80-90
B: Through the bowel wall - 60
C: Regional lymph nodes metastasis - 30
D: Distant metastases - <5
What are the symptoms of colorectal carcinoma?
Left-sided
- Change in bowel habit
- Bleeding +/- mucous
- Tenesmus (if rectal mass)
- Change in stool form (small calibre or ribbon-like stools)
Right sided
- Later presentation with symptoms of
- Anaemia
- Weight loss
- Malaise
- +/- Pain
20% of tumours present as emergency with pain and distension caused by large bowel obstruction, haemorrhage and peritonitis as a result of perforation
What are the signs of colorectal adenocarcinoma on examination?
- Anaemia may be the only sign if right-sided
- Abdominal mass
- Low-lying rectal tumours palpable on DRE
- Metastatic disease: hepatomegaly, “shifting dullness” ascites
- Weight loss
- Fistula
When should you do a 2WW referral for suspected colorectal cancer?
- _>_40yrs with unexplained weight loss + abdominal pain, OR
- _>_50yrs with unexplained rectal bleeding, OR
- _>_60yrs with:
- Iron-deficiency anaemia, OR
- Changes in their bowel habit, OR
- Occult blood in their faeces
If younger but presenting with a combination of abdominal pain, change in bowels, weight loss and Fe deficiency.
What investigations would you do for colorectal carcinomas?
Blood
- FBC - ?anaemia
- LFT - normal, often even when liver metastases present
- U&Es - N unless compression of ureters
- Stool - occult or frank blood in stool can be used for screening
Imaging
- CT - may show colonic wall thickening, enlarged lymph nodes, liver metastases, ascites, lung secondaries
- PET scan - focal areas of uptake of 18-fluoro-2-deoxyglucose (FDG) detects malignancy
- Abdominal ultrasound scan - for hepatic metastases
Invasive
- Endoscopy/sigmoidoscopy/colonoscopy +/- biopsy - ulcerating or exophytic mucosal lesion that may narrow the bowel lumen. Or used for polypectomy.
- Barium contrast studies - “apple core” stricture on barium enema
NB: CEA - should only be measured AFTER confirmation of the colorectal cancer; not sensitive or specific enough for screening or diagnosis ; used for monitoring treatment
What is shown?
The photo shows a typical colonic carcinoma stenosing and obstructing the lumen of the colon.
What are these Dukes’ stages?
Dukes’ A - Tumour confined to bowel wall
B - Tumour has invaded beyond bowel wall but there is no lymph node metastasis
C1- Tumour has metastasized to lymph nodes but not to the highest node
C2 - Tumour has metastasized to the highest lymph node
D - Tumour has metastasized to other organs
Dilated transverse colon
NB: lack of small bowel loops on the radiograph – this implies a competent ileocaecal valve, which increases the risk of colonic perforation.
What is this stricture called and what is it characteristic of?
Apple core stricture
Colonic carcinoma
List 3 familial syndromes with colorectal polyps.
- Peutz-Jeghers syndrome
- FAP - Gardner’s, Turcot
- HNPCC
What is the inheritance of FAP?
Autosomal dominant - onset at 25yrs
Mutated APC tumour suppressor gene → minimum 100 polyps
What are the distinctive features of Gardner syndrome?
Osteomas of skull and mandible
Epidermoid cysts
Desmoid tumours
Dental caries
Supernumerary teeth
Mesenteric fibromatoses
How is HNPCC/Lynch syndrome inherited?
Autosomal dominant → colorectal cancer at early age usually due to carcinoma proximal to splenic flexure
NB: YOU DO NOT NECESSARILY GET POLYPS IN THIS CONDITION
What are the risk factors for colorectal cancer?
- Age (if <50yrs probably familial)
- Western populations
- Poor diet
- No exercise
- Obesity
- Chronic IBD
What type are most colorectal cancers?
98% adenocarcinomas
What is the pathophysiology of most colorectal cancers?
Adenoma-carcinoma sequence
- Adenomas/polyps tend to appear about 10yrs before carcinomas
- Screening and removal of adenomas reduces risk of cancer
- Any polyp that is large (>4cm), which has high villous component and more dysplastic change has higher risk of carcinoma
What are the most common sites of metastases from colorectal cancer?
Liver
Lungs
What screening is available for colorectal cancer?
Every 2yrs between 60-74yrs using home faecal immunochemical kit. Although there is now gradual move to start this screening from age 50yrs.
If abnormal results then colonoscopy needed
If no polyps → rescreen in 10yrs
If negative stools → rescreen in 1yr
What is the management of colorectal cancer?
Rectal cancers
Lower third rectal:
- Transanal resection of tumour
- If positive margins → definitive surgery i.e. low anterior or abdominoperineal resection
- Adjuvant chemo/radiotherapy
Upper third rectal:
- Anterior resection + sphincter preservation with colorectal/coloanal anastomosis
- Adjuvant chemo/radiotherapy
Colon cancer:
- Surgical resection - with min. 12 nodes removed for staging
- Chemotherapy
Not suitable for surgery:
- Chemotherapy - FLOZ or FOLFIRI
- Anti-VEGF - bevacizumab improves survival
- Stenting
What is the name of the anterior resection procedure for upper rectal cancers?
Hartmann’s
What is the surgical approach for right vs left colon cancers?
RIGHT
Right Hemicolectomy or Extended Right Hemicolectomy
- For caecal tumours or ascending colon tumours; extended option for transverse colon.
- During the procedure the ileocolic, right colic, and right branch of the middle colic vessels (branches of the SMA) are divided and removed with their mesenteries
LEFT:
Left Hemicolectomy
- For descending colon tumours.
- Similar to the right hemicolectomy, the left branch of the middle colic vessels (branch of SMA/SMV), the inferior mesenteric vein, and the left colic vessels are divided and removed with their mesenteries
What are the complications of colorectal cancer?
Bladder dysfunction/ED with rectal excision due to pelvic nerve damage
Low anterior resection syndrome - faecal incontinence or urgency, and emptying difficulties after anterior resection
What is the prognosis with colorectal cancers?
