Colorectal Cancer Flashcards
Epidemiology
Fourth most common cancer in the UK
Second highest mortality of any cancer
Strongly associated with age but can occur as young as 20yrs particularly in patients with inherited cancer syndromes.
Most common type of colorectal cancer
Adenocarcinoma
Rare types include lymphoma, carcinoid and sarcoma.
Adenoma-carcinoma sequence
Progression of normal mucosa to colonic adenoma (colorectal polyps) to adenocarcinoma.
This is called the adenoma-carcinoma sequence.
Progression to adenocarcinomas occurs in approx 10% of adenomas.
What genetic mutations predispose to colorectal cancer?
Adenomatous polyposis coli (APC) which is a TSG that is associated with Familial adenomatous polyposis (FAP)
Hereditary nonpolyposis colorectal cancer (HNPCC) which is a DNA mismatch repair gene associated with Lynch syndrome
Risk factors
75% are sporadic with no specific risk factors
Increasing age
FH
IBD
Low fibre diet
High processed meat intake
Smoking
High alcohol intake
Common clinical features regardless of where the bowel cancer is.
Change in bowel habits
Rectal bleeding
Weight loss
Abdo pain
Iron-deficiency anaemia
Clinical features of right-sided colon cacer
Abdo pain
Occult bleeding/anaemia
Mass in right iliac fossa
Often present late
Clinical features of left-sided colon cancer
Rectal bleeding
Change in bowel habits
Tenesmus
Mass in left iliac fossa or on PR exam
When should patients be referred for urgent investigation?
>40y with unexplained weight loss and abdo pain
>50 with unexplained rectal bleeding
>60y with ID anaemia or change in bowel habits
+ve occult blood screening test
Dx
IBD
Haemorrhoids
Explain colorectal cancer screening
Every 2 years to men and women aged 60-75 years
Faecal immunochemistry (FIT) is used to check for antibodies vs human haemoglobin to detect blood in faeces.
+ve patients are offered further investigations via colonoscopy.
Laboratory tests
FBC that might show microcytic anaemia (ID)
LFTs
Clotting
Carcinoembryonic antigen (CEA) should not be used as a diagnostic test due to its poor sensitivity and specificity. It is only useful in monitoring treatment efficacy and disease recurrence.
What is the gold standard for diagnosis?
Colonoscopy with biopsy
If a colonoscopy is not suitable for the patient a flexible sigmoidoscopy or CT colonography can be performed instead.
Once diagnosis is done, what other imaging should be done?
CT abdo-chest-pelvis to look for distant metastases and local invasion.
MRI rectum (only for rectal cancers) to check for depth of invasion and potential need for pre-operative chemotherapy
Endo-anal USS for early rectal cancers in T1 or T2 only to check for suitability for trans-anal resection.
What staging is used in colorectal cancer?
Dukes’ staging as well as TNM staging.
Explain Dukes’ staging
A - Confined beneath the muscularis propria
B - Extension through the muscularis propria
C - Involvement of regional LN
D - Distant metastases
General management
Discussed with MDT
Only definitive curative option is surgery
Chemo and radiotherapy have important roles as neoadjuvant and adjuvant treatments
What is the main idea of surgical intervention.
Regional colectomy with removal of primary tumour + adequate margins and lympathic drainage.
This is then followed by primary anastomosis or formation of a stoma.
What is the surgical approach for caecal tumours or ascending colon tumours +/- transverse colon tumours.
Right hemicolectomy or extended right hemicolectomy.
The ileocolic, right colic, right branch of the middle colic vessels from the SMA are divided and removed with their mesenteries.
What is the surgical approach for descending colon tumours?
Left hemicolectomy
The left branch of the middle colic vessels (SMA/SMV) the inferior mesenteric vein and the left colic vessels (branhces of the IMA/IMV) are divided and removed with their mesenteries.
What is the surgical approach for sigmoid colon tumours?
Sigmoidcolectomy
IMA is fully dissected out with the tumour in order to ensure adequate margins are obtained
What is the surgical approach for high rectal tumours (>5cm from the anus)
Anterior resection.
This leaves the rectal sphincter intact if an anastomosis is performed
A loop ileostomy is commonly performed to protect the anastomossis and reduced complications of anastomotic leak.
What is the surgical approach for low rectal tumour (<5 cm from anus)
Abdominalperineal (AP) resection
Excision of the distal colon, rectum and anal sphincter resulting in a permanent colostomy
Explain Hartmann’s procedure
Used in emergency bowel surgery like obstruction or perforatoion.
There is complete resection of the recto-sigmoid colon with formation of an end colostomy and closure of the rectal stump
Chemotherapy
Typically indicated in pateitns with advanced disease (Dukes’ C to D)
FOLFOX with folinic acid, fluorouracil (5-FU) and Oxaliplatin
Radiotherapy
Used in rectal cancer (not in colon cancer due to risk of damage to small bowel)
Most often neo-adjuvant treatment.
It is particularly useful in rectal cancers with threatened circumferential resection on MRI.
Palliative care
Very advanced colorectal cancers will be managed palliatively with focus on reducing cancer growth and symptom control.
Examples of palliative care
Endoluminal stenting to relieve acute bowel obstruction in left-sided colorectal cancer
Stoma formation in acute obstruction
Resection of secondaries (not commonly performed)
