Colorectal Flashcards
how common is colorectal cancer?
4th most common cancer in UK - 40,000 new cases a year
2nd highest mortality of any cancer
where does colorectal cancer originate from and what is the most common type?
epithelial cells lining the colon or rectum and is most commonly an adenocarcinoma
(rare lymphoma, carcinoid and sarcoma)
how do most colorectal cancers develop?
progression of normal mucosa to colonic adenoma to invasive adenocarcinoma
adenomas can be present for 10 years before they become malignant
progression to adenocarcinoma occurs in 10% of adenomas
what are the genetic mutations associated with predisposing individuals to colorectal cancer?
- Familial adenomatous polyposis - malfunctioning Adenomatous polyposis coli (APC)
- Hereditary nonpolyposis colorectal cancer (HNPCC)
what is Familial adenomatous polyposis?
autosomal dominant condition involving malfunctioning tumour suppressor genes called Adenomatous polyposis coli (APC)
results in polyps (adenomas) developing in the large intestine - polyps have potential to become cancerous
pt have their entire large intestine removed prophylactically to prevent development of bowel cancer - panproctocolectomy
what is HNPCC?
autosomal dominant
results from mutations in DNA mismatch repair genes
patients are at higher risk of number of cancers - esp colorectal
risk factors of colorectal cancer
- 75% are sporadic
- increasing age
- family history
- inflammatory bowel disease
- low fibre diet
- high processed meat intake
- smoking
- high alcohol intake
- obesity and sedentary lifestyle
clinical features of colorectal cancer
- Change in bowel habit
- Rectal bleeding
- Weight loss (associated with metastatic disease)
- Abdominal pain
- Iron-deficient anaemia
- Abdominal or rectal mass on examination
features of right-sided colon cancer
abdominal pain
occult bleeding/anaemia
mass in RIF
often presents late
features of left-sided colon cancer
rectal bleeding
change in bowel habit
tenesmus
mass in LIF or on PR exam
what is the NICE guidance on referring ? bowel cancer?
- ≥40yrs with unexplained weight loss and abdominal pain
- ≥50yrs with unexplained rectal bleeding
- ≥60yrs with iron‑deficiency anaemia or change in bowel habit
- Positive occult blood screening test
how may someone with bowel cancer present acutely?
obstruction if the tumour blocks the passage through the bowel
surgical emergency - vomiting, abdo pain, absolute constipation
what are some differentials for colon cancer?
inflammatory bowel disease - average age of onset 20-40 yrs, typically presents with bloody, mucusy diarrhoea
haemorrhoids - bright red rectal bleeding on surface of stool but rarely presents with pain, altered bowel habits or weight loss
when is screening for bowel cancer offered in the uk?
every 2 years to men and women aged 60-74
what test is used in bowel cancer screening?
faecal immunochemistry test (FIT)
(supersedes faecal occult test)
uses antibodies against human haemoglobin to detect blood in faces
what is FIT and how does it work?
uses antibodies against human haemoglobin to detect blood in faces
can be used in GP to assess for bowel cancer in pt who do not meet criteria for 2ww
what happens if a patients FIT sample is positive?
offered an appointment with a specialist nurse to further investigate via colonoscopy
The NHS Bowel Cancer Screening Programme has increased detection of colorectal cancer in people aged 60-69 by what %?
11%
what laboratory tests are required?
routine bloods - FBC + may show microcytic (iron-deficiency) anaemia, LFTS & clotting
tumour markers NOT USED
why is the tumour marker Carcinoembryonic Antigen (CEA) not used as a test?
poor sensitivity and specificity
what is Carcinoembryonic Antigen (CEA) used for?
monitoring disease progression - conducted pre and post treatment
may be used for predicting relapse in patients previously treated for bowel cancer
what is the gold standard for diagnosis of colorectal cancer?
colonoscopy with biopsy
involves endoscopy to visualise the entire large bowel
biopsy suspicious lesion or tattoo in preparation for surgery
why might colonoscopy not be suitable for a patient?
frailty
co-morbidities
intolerance
what is used in patients who cannot tolerate colonoscopy?
flexible sigmoidoscopy - rectum and sigmoid colon only - may be used when there is only rectal bleeding - risk of missing cancers in other parts of the colon
CT colonography - ct scan with bowel prep and contrast to visualise the colon in more detail - less detail and does not allow for biopsy
what investigations are required for staging once the diagnosis has been made?
- *CT scan** - chest abdo pelvis to look for distant metastases and local invasion full colonoscopy or CT colonogram is required to check for a 2nd (synchronous) tumour if not used initially)
- *MRI rectum** (rectal cancers only)- depth and invasion and potential need for pre-op chemotherapy
- *endo-anal USS** (T1 or T2 rectal caner) - asses suitability for trans-anal resection
what staging is used for colorectal cancer?
TNM system (like most cancers) T = depth the tumour invades the bowel wall N = extent of spread to local lymph nodes M = metastasis or not Dukes staging used in some places
what are the Dukes’ stages and their associated survival %
been replaced by TNM
A = Confined beneath the muscularis propria = 90% 5 year survival B = Extension through the muscularis propria = 65% 5 year survival C = Involvement of regional lymph nodes = 30% 5 year survival D = distant metastasis = \<10% 5 year survival
describe the TNM staging
T for Tumour:
- TX – unable to assess size
- T1 – submucosa involvement
- T2 – involvement of muscularis propria (muscle layer)
- T3 – involvement of the subserosa and serosa (outer layer), but not through the serosa
- T4 – spread through the serosa (4a) reaching other tissues or organs (4b)
N for Nodes:
- NX – unable to assess nodes
- N0 – no nodal spread
- N1 – spread to 1-3 nodes
- N2 – spread to more than 3 nodes
M for Metastasis:
- M0 – no metastasis
- M1 – metastasis
what is the curative management of colon cancer?
surgery - suitable regional colectomy to ensure removal of the primary tumour with adequate margins and lymphatic drainage followed by primary anastomosis or formation of a stoma
what is a right hemicolectomy or extended right hemicolectomy and when is it used?
- caecal tumours or ascending colon tumours
- removal of caecum, ascending and (proximal) transverses colon
- extended option performed for any transverse colon tumours.
- During procedure the ileocolic, right colic, and right branch of the middle colic vessels (branches of the SMA) are divided and removed with their mesenteries.
what is a left hemicolectomy and when is it used?
- descending colon tumours
- removal of distal transverse and descending colon
- 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 (branches of the IMA/IMV) are divided and removed with their mesenteries.
what is a sigmoidcolectomy - aka high anterior resection
- sigmoid colon tumours.
- remove sigmoid colon
- In this instance, the IMA is fully dissected out with the tumour in order to ensure adequate margins are obtained
what is a low anterior resection?
removal of sigmoid colon and upper rectum but sparing lower rectum and anus
what is an abdominoperineal resection (AP) and when is it used?
low rectal tumours, typically <5cm from the anus.
This technique involves excision of the distal colon, rectum and anal sphincters, resulting in a permanent colostomy
What is Hartmann’s Procedure and when is it used?
emergency bowel surgery - in bowel obstruction or perforation
complete resection of the recto-sigmoid colon with the formation of an end colostomy and the closure of the rectal stump
colostomy can be permanent or reversed at a later date
what are some complications associated with bowel cancer surgery?
- Bleeding, infection and pain
- Damage to nerves, bladder, ureter or bowel
- Post-operative ileus
- Anaesthetic risks
- Laparoscopic surgery converted during the operation to open surgery (laparotomy)
- Leakage or failure of the anastomosis
- Requirement for a stoma
- Failure to remove the tumour
- Change in bowel habit
- Venous thromboembolism (DVT and PE)
- Incisional hernias
- Intra-abdominal adhesions
what is low anterior resection syndrome?
may occur after resection of portion of bowel from the rectum, with anastomosis between colon and rectum
can result in a number of symptoms:
- urgency and frequency of bowel movements
- feacal incontinence
- difficulty controlling flatulence
when is chemotherapy indicated?
patients with advanced disease
what is an example of a chemotherapy regime for patients with metastatic colorectal cancer?
FOLFOX
Folinic acid
Fluorouracil
Oxaliplatin
demonstrated to significantly improve 3 year disease free survival for patients with advanced colon cancer
why is radiotherapy rarely used in colon cancer and when is it used?
- risk of damage to the small bowel
- used as neo-adjuvant treatment
- used for patients with rectal cancers which look on MRI to have threatened circumferential resection. undergo pre op long course chemo-radiation to shrink tumour - increases chance of complete resection and cure
what is the focus of palliative care in colon cancer?
reducing cancer growth and ensuring adequate symptom control
can have surgery to reduce symptoms and reduce size of tumour
what are the palliative care options for patients with colon cancer?
endoluminal stenting - relieve acute bowel obstruction in patients with left-sided tumours
stoma formation - acute obstruction relief
resection of secondaries - can be done with adjuvant chemotherapy for any liver mets
