GI - Colorectal cancer Flashcards
CRC
Epidemiology
Typical sites
Modes of metastasis
Epidemiology:
- > 90% of CRC occurs in patients age ≥ 50
- M: F ratio = 1.3: 1
- Commonest cancer in Hong Kong
- 2nd leading cause of cancer death in both males and females
Typical sites: Majority of CRC are left-sided cancer
- Ascending colon = 25%
- Transverse colon = 10%
- Descending colon = 15%
- Sigmoid = 20%
- Rectum = 30%
Modes of metastasis: Hematogenous/ Lymphatic/ Contiguous/ Transperitoneal
- Liver is usually the first site of metastasis since the venous drainage of intestinal tract
is via the portal venous system
- Lung can be the first site of metastasis for tumours in distal rectum since inferior rectal veins drains into IVC rather than portal venous system
CRC
Risk factors
Non-modifiable:
- Asian or Ashkenazi Jews
- Old age
Past medical history (PMH)
- Previous colorectal cancer (CRC)
- Colonic adenomatous polyps
- Hereditary colorectal cancer syndrome
* Familial adenomatous polyposis (FAP)
* Hereditary non-polyposis colorectal cancer (HNPCC) (Lynch syndrome)
* Familial juvenile polyposis
* MYH-associated polyposis
* Hamartoma polyposis
- Inflammatory bowel disease
- Obesity
- Diabetes mellitus (DM)
Family history:
- Colorectal cancer (4x risk)
- Colonic adenomatous polyps
Social history:
- Smoking
- Alcoholism
- Lack of physical exercise
- Dietary lifestyle
* Red and processed meat
* Lack of dietary fibers
* High temperature cooking
Familial adenomatous polyposis (FAP)
Inheritance
Variants
Genetic cause
Disease course
Inheritance:
- Autosomal dominant (AD) syndrome
- Up to 25% present without other affected family members
Variants:
- Gardner’s syndrome = FAP associated with extracolonic manifestation
- Turcot’s syndrome = FAP associated with CNS tumours
- Attenuated FAP = < 100 adenomatous colorectal polyps at presentation
Genetics:
- germline mutations in adenomatous polyposis coli (APC) gene on chromosome 5
- APC gene is a tumour suppressor gene
Disease course:
- Polyp and symptoms appear at an average age of 16 (2nd – 3rd decades of life)
- Colorectal cancer occurs in 90% of untreated individuals at the age of 45 and approaches ~100% by 50 years old
- > 100 adenomatous colorectal polyps
- Adenomatous polyps do NOT have high malignant potential individually
- Increased risk of CRC due to vast number of adenomatous polyps
Familial adenomatous polyposis (FAP)
Extracolonic manifestations
Familial adenomatous polyposis (FAP)
Investigations
Investigation: Mainly by colonoscopy
- Colonoscopy showing > 100 polyps in addition to extra-colonic tumours of duodenum and
pancreas (ampullary carcinoma)
Genetic testing:
- APC genetics testing of at-risk family members
Surveillance:
- Flexible sigmoidoscopy every 1 year (annual) starting at age 12
- OGD every 1 – 3 years starting at age 25: for adenocarinoma in any part of GIT especially duodenum
Familial adenomatous polyposis (FAP)
Treatment options
Surgical treatment:
Total proctocolectomy with end ileostomy
Total proctocolectomy with ileal-pouch anal anastomosis (IPAA):
- Indicated for profuse polyposis without rectal sparing/ >10 rectal adenomas
- Indicated for mesenteric desmoid tumours (cannot convert IRA to IPAA later due to shortened mesentery)
- Higher risk of bleeding and infertility in women
Total abdominal colectomy with ileorectal anastomosis (IRA)
- Indicated if rectal sparing/ <10 rectal adenoma + all polyps managed endoscopically by colonoscopic snare excision
- May progress to severe rectal polyposis and require a secondary proctectomy
Hereditary non-polyposis colorectal cancer (HNPCC)
Inheritance
Genetic cause
Disease course
Inheritance:
- Autosomal dominant (AD) syndrome
Genetic cause: Amsterdam criteria for Lynch syndrome
- patients and family with a germline mutation in one of the DNA mismatch repair (MMR) genes: MLH1 (90%), MSH2, MSH6 (10%), EPCAM gene
Disease course:
- 70 – 80% of affected individuals will develop CRC
- Mean age of colorectal cancer at age 40 – 45 with some presenting in their 20s
Hereditary non-polyposis colorectal cancer (HNPCC)
Clinical manifestations
Diagnostic criteria
CRC:
- Predominant right sided
- Arise from large/ flat/ dysplastic adenomas
- Rapid progression from adenomas
Extra-colonic manifestation
o GI: Gastric/ Pancreas/ Biliary/ Small intestine
o Gyn: Endometrial/ Ovarian
o Uro: Renal/ Ureter
o CNS: Brain (glioma)
o Others: Sebaceous gland
Amsterdam criteria: 3-2-1 rule
- 3 or more relatives with Lynch syndrome associated cancer
- 2 or more successive generations should be affected
- 1 or more cancers were diagnosed before age of 50
- Familial adenomatous polyposis should be excluded in CRC
- Tumour should be verified by pathological examination
Hereditary non-polyposis colorectal cancer (HNPCC)
Investigations and surveillance
Management
Surveillance
- Colonoscopy: Starting at age 20 every 1 year
- OGD with biopsy of gastric antrum: Starting at age 30 every 1 – 2 years
- USG kidney and bladder: Starting at age 30 every 1 – 2 years
- Pelvic examination, endometrial biopsy, ransabdominal/transvaginal USG and CA125: Starting at age 30 every 1 year
Treatment
* Total abdominal colectomy with ileorectal anastomosis (IRA)
* Total abdominal hysterectomy and bilateral salpingo-oophorectomy (TAHBSO)
Colon
Vascular supply and lymphatics
Rectum
Anatomical boundaries
Anatomical features
Divisions
Neurovascular and lymphatics
Anatomical: Measuring 12 – 15 cm long starting from rectosigmoid junction to dentate line
o Radiographic: Sacral promontory is the upper limit of rectum
o Endoscopic: 15 cm from anal verge is the upper limit of rectum
Anatomical: Absence of taeniae coli, epiploic appendices and haustration; NOT suspended by a true mesentery
Mesorectum: perirectal areolar tissue that is thicker posteriorly and contains terminal branches of IMA
Divisions:
- Upper 1/3 = Covered by peritoneum anteriorly and laterally
- Middle 1/3 = Covered by peritoneum anteriorly only
- Lower 1/3 = Completely extra-peritoneal lying below pelvic peritoneum
Anal canal
Anatomical boundaries
Neurovascular and lymphatic supply
Anatomical definition of rectal cancers
Anal canal
* Measuring 4 cm long from the anal verge
* Dentate (Pectinate) line divides upper 2/3 and lower 1/3 of anal canal
Location of rectal cancer
* Lower rectal cancer = 4 – 8 cm from anal verge
* Middle rectal cancer = 8 – 12 cm from anal verge
* Upper rectal cancer = 12 – 15 cm from anal verge
CRC
Pathogenesis pathways
Adenoma-carcinoma sequence (60 – 70% of sporadic cancer): Chromosomal instability pathway
- arise from adenomatous polyps (2/3 all polyps) by accumulation of mutations and transform into adenomas
- Progression from adenoma to carcinoma takes at least 10 years on average
- Villous adenomas are associated with highest malignancy risk: up to 40%
- Other adenomas e.g. tubular, hyperplastic, non-polypoid adenomas have lower risk of malignant change
- Associated genetic changes: Acitvation of K-ras oncogene, Inactivation of APC and p53 tumour suppressor genes, Mutation of MYH repair gene
Microsatellite instability pathway (MSI) (15% of sporadic cancer)
- Strongly associated with HNPCC
- Includes MSH2, MLH1, PMS1, PMS2, MSH6/GTBP
- Instability promotes mutation, genomic instability and ultimately to carcinogenesis
CRC
TNM staging
TNM:
- Stage I = Tumour that is invasive through the muscularis mucosae but are confined to the
submucosa (T1) or muscularis propria (T2) in the ABSENCE of nodal metastasis
- Stage II = Tumour that invades through bowel wall into Subserosa or non-peritonealized pericolic or perirectal tissues (T3) or into other organs or tissues or through the visceral peritoneum (T4) in the ABSENCE of nodal metastasis
- Stage III = Presence of nodal metastasis with any T stage
- Stage IV = Presence of distant metastasis
Duke’s staging (superceded by TNM)
- Duke’s A = Tumour within wall of the bowel
- Duke’s B = Tumour invades through the wall of bowel
- Duke’s C = Presence of regional LN metastasis
- Duke’s D = Presence of distant metastasis
Colorectal polyp
Types and malignant potential
- Inflammatory pseudopolyp: No malignant potential
- Inflammatory reaction to muscosal ulcersations and regenerations in Inflammatory bowel disease - Haramtomatous: No malignant potential
- Juvenile polyp: young onset, might require polypectomy
- Peutz-Jeghers polyps: Associated with the Peutz-Jeghers syndrome (PJS) due to STK11 mutations - Serrated:
- Hyperplastic (most common non-neoplastic polyp): no malignant potential except subtype hyperplastic polyposis
- Sessile serrated polyp/ adenoma (SSP/A): Malignant potential, precursor lesion to sporadic microsatellite
instability-high (MSI-H) colon cancer
- Traditional Serrated Adenoma (TSA): malignant potential, prevalent in rectocigmoid colon
Adenomatous polyp: Malignant potential
- Endoscopic types: Sessile, Flat, Depressed, Pedunculated
- Histological types: Tubular (80% CRC), Villous (5-15% CRC), Tubulovillous (5-15% CRC)
- Malignant potential: Sessile > Pedunculated; Villous > Tubular
Classification for malignant colorectal polyps
Haggitt classification (1985) of pedunculated malignant colorectal polyps
Kudo (Kikuchi) classification of sessile malignant colorectal polyps
High risk features of malignant colonic polyps
High risk feature:
- associated with an increased incidence of LN
metastasis and residual cancer
- need for radical resection
List:
* Poorly differentiated histology
* Lymphovascular invasion
* Inadequate endoscopic resection margin < 2 mm
* T1 lesion with invasion into the lower 1/3 of the submucosa (Sm-3)
* T2 lesion or above with invasion through the muscularis propria
CRC
Clinical presentation
Clinical presentation:
- PR bleeding
- Melena
- Hematochezia
- Abdominal pain
* Partial or complete obstruction
* Peritoneal dissemination
* Intestinal perforation leading to generalized peritonitis
- Abdominal distention
- Change in bowel habit
- Tenesmus
- Diminished caliber of stool
- Lymphadenopathy
-Anemic symptoms - Pallor/ Palpitations/ Dyspnea
- Constitutional symptoms
- Nausea and vomiting
- Anorexia and weight loss
CRC
Investigations
Biochemical
- CBC with differential: Anaemia of various cases
- Iron profile: IDA
- LFT: liver metastasis, nutritional status via albumin level
- RFT: contrast imaging, dehydration/ hypovolemia
- CEA level: Pre-operative checkup to facilitate surgical planning, baseline and Post-operative follow-up to detect recurrence or metastasis, Assessment of prognosis
- Genetic test: Molecular profiling for microsatellite instability (MSI)/ deficient DNA mismatch repair (dMMR) - MSI/dMMR phenotype has poorer differentiation, different response to adjuvant 5-FU, better prognosis in stage-adjusted survival
Imaging:
- Colonoscopy: localize and biopsy lesions
- CT virtual colonoscopy: Indicated in incomplete colonoscopy due to mechanical obstruction or patient’s intolerance
- Double-contrast barium enema is used (DCBE)/ Gastrografin contrast enema: Indicated when colonoscopy is unsuccessful due to intestinal obstruction; “Apple-core” appearance
Staging investigations:
- CXR: cardiopulmonary diseases, metastatic lesions
- CT chest + abdomen + pelvis (T + A + P): demonstrate tumour extension, regional lymphatic and distant metastasis and tumour-related complications
- CT chest and MRI liver
- Transrectal ultrasound (TRUS) for staging rectal tumors to evaluate depth of invasion, circumferential resection margin (CRM) and LN status to determine need of neoadjuvant chemoradiation
- MRI rectum: assess mesorectal involvement for neoadjuvant chemoirradiation
- PET scan (FDG): distant metastasis and recurrence in follow-up
CRC
Medical treatment options
Predictive biomarker testing:
- KRAS screening: Wild-type KRAS has a favorable response to EGFR-targerted therapies - cetuximab or panitumumab. Mutant KRAS will NOT benefit
- BRAF screening: Mutant BRAF is unlikely to benefit from cetuximab or panitumumab
Medical treatment:
Cytotoxic chemotherapy: Indicated for all stage III and high-risk stage II disease (e.g. T4 stage, poor differentiation, perineural or lymphovascular invasion)
- 5-fluorouracil/ leucovorin (5-FU) (OR)
capecitabine (Xeloda) + oxaliplatin (OR) irinotecan
- S/E: Mucositis/ Nausea and vomiting/ Diarrhea/ Febrile neutropenia/ Alopecia/ Hand-foot syndrome
Anti-VEGF monocolonal antibodies: indicated only for stage IV metastatic disease
- Add-on therapy to chemotherapy for KRAS/ BRAF mutations
- Bevacizumab (OR) Aflibercept (OR) Regorafenib
Anti-EGFR monoclonal antibodies: indicated only for stage IV metastatic disease
- Add-on therapy for Irinotecan-based chemotherapy for Wild-type KRAS/ BRAF
- Cetuximab (OR) Panitumumab
CRC - colon cancer
Surgical treatment options
Goals:
- Complete removal of tumour with adequate proximal and distal margin (at least 5cm)
- High ligation of arterial pedicle for LN clearance
- Tension-free anastomosis
- Good anastomotic/ stoma blood supply
LN resection for staging: minimum of 12 lymph nodes
Stage-specific treatment:
- Stage I = Surgical resection
- Stage II = Surgical resection ± Adjuvant chemotherapy for high risk factors (young patients, inadequate LN retrieval (< 12) or tumours with “high-risk” histological findings)
- Stage III = Surgical resection + Adjuvant chemotherapy (improves survival due to LN involvement, except patients with MSI-high stage III disease)
- Stage IV = Resection in highly selected patients + Adjuvant chemotherapy/ Palliative procedures
Patient selection in Stage IV disease:
- Liver metastasis: only 20% of metastasis confined to liver is potentially resectable for cure. All patients with liver met need adjuvant chemotherapy
- Lung metastasis: only 2% of metastasis is resectable for cure
Palliative care:
- Colonic stenting/ Diverting stoma/ Bypass surgery for obstruction
- Angiographic embolization for hemorrhage
- External beam irradiation
Extents of bowel resection
General rule: malignancy indicates ligation of vessels at their origin
- Segmental colectomy: cut descending colon with left colic branches
- Ileocecectomy: cut distal ileum and cecum with ileal branch of ileocolic artery
- Right hemicolectomy (benign): cut distal ileum, cecum, ascending colon, transverse colon to the right of middle colic artery + ileal and colic branches of ileocolic artery + right colic artery + branch of middle colic artery
- Right hemicolectomy (malignant): cut distal ileum, cecum and ascending colon, transverse colon to the right of middle colic artery + ORIGIN of ileocolic, right colic, middle colic artery and vein
- Extended right hemicolectomy: same as right hemocolectomy (malignant) + extend towards splenic flexure of transverse colon
- Transverse colectomy (usually do extended right hemicolectomy instead): cut from hepatic to splenic flexure of transverse colon, root of middle colic and left colic arteries
- Left hemicolectomy (benign): cut splenic flexure of transverse colon, descending colon and sigmoid colon above rectosigmoid junction + Branches of left colic artery + branches of sigmoid artery
- Left colectomy (malignant): cut splenic flexure of transverse colon, descending colon, and sigmoid colon below rectosigmoid junction + Origin of IMA and IMV
- Total colectomy: entire intraperitoneal colon from terminal ileum to below rectosigmoid junction with associated mesentery + All mesenteric vessels ligated close to origin
Compare open vs laparoscopic vs robotic colectomy
Laparoscopic colectomy:
- Uncomplicated localized colorectal
cancer
- No prior extensive abdominal surgery
Open colectomy:
- complicated colorectal cancer
Choice of colectomy for benign, malignant lesions and malignant polyps
Benign:
- Segmental colectomy, Left or right hemicolectomy
- Diverticular disease: Sigmoidectomy or Left hemicolectomy if descending colon cannot anastomose
- Mesenteric vessels are ligated blose to mesenteric border of colon
- Unnecessary to resect draining lymph node
Malignant lesions:
- Cecum, appendix, ascending colon: Right hemicolectomy
- Hepatic flexure, proximal to mid-transverse colon: Extended right hemicolectomy
- Distal transverse colon, splenic flexure or descending colon: Left hemicolectomy
- Sigmoid colon: sigmoidectomy
- Complete mesocolic resection + ligation of mesenteric vessels close to origin to optimally resect lymphovascular tissue
Malignant polyp:
- Indicated for types of Sessile polyps and adenomatous polyps with malignant potnetial
- High risk features: poorly differentiated histology, lymphovascular invasion, cancer at
resection or stalk margin, invasion into muscularis propria (T2 lesion), sessile polyp with lower third submucosal penetration
Choice of anastomosis after colectomy
Primary anastomosis without temporary proximal diverting ostomy
- Uncomplicated cases
- Right or extended right hemicolectomy (lower bacteria count)
Primary anastomosis with temporary proximal diverting ostomy
- Complicated cases: obstruction, perforation, localized peritonitis
- Proximal diverting ostomy include loop ileostomy, loop colostomy or end ostomy
- Left hemicolectomy (high risk of anastomotic leakage) benefits from proximal diversion to lower complication rate and risk of reoperation for anastomotic leakage
No primary anastomosis:
- Medically unstable
- Diffuse peritonitis
- Free perforation
Complications of colectomy
General complications (Early < 30 days)
- Surgical site infection
- Postoperative ileus
Intra-abdominal complications (Immediate)
- Anterior resection syndrome: Fecal frequency, urgency, clustering or incontinence
- GI: Splenic/ Duodenal/ Pancreatic/ Gastric injury
- UG: Ureteral/ Bladder/ Urethral injury
Anastomotic complications:
- Bleeding: give blood transfusion and correct coagulopathy
- Leakage (intraperitoneal/ extraperitoneal): give fluid resuscitation and broad-spectrum IV antibiotics, bowel
rest, image-guided percutaneous drainage of abscess, temporary fecal diversion or drainage, resection of the anastomosis
- Stricture: observe, finger dilatation for low anastomosis and endoscopic balloon dilatation for high anastomosis
- Fistula (Enterocutaneous, rectovaginal, and rectourinary fistula): Enterocutaneous fistula can be managed by conservation; Rectovaginal or rectourinary fistula should be managed with proximal fecal diversion
CRC
Prevention and surveillance
Lifestyle modifications:
- Physical activity
* Perform ≥ 150 mins of physical activity per week
- Dietary changes
* ↑ Intake of dietary fibers (e.g. whole-grains, beans, fruits and vegetables)
* ↓ Intake of red and processed meat (e.g. sausage, ham, bacon and luncheon meat)
- Avoid alcohol and smoking
Surveillance:
Stool-based tests
- Guaiac-based fecal occult blood test (gFOBT)
- Fecal immunochemical test (FIT)
- Fecal DNA test
Direct visualization tests
- Colonoscopy
- Flexible sigmoidoscopy
- Capsule endoscopy
- CT colonography (colonic imaging)
Fecal immunochemical tests (FIT)
MoA
Sampling
Advantage and disadvantage
MoA:
- detect only human globin and thus do NOT detect upper GI bleeding since the globin is digested during the transit (more specific to lower GI bleeding)
- Food with peroxidase activity also do not produce a positive reaction
Sampling:
- Only 1 stool sample is required for automated analysis
- Sensitivity of test decreases with mailing, delayed processing after sampling and exposure to high ambient temperature due to Hb degradation
A
Fecal DNA test
MoA
Sampling
Advantage and disadvantage
MoA:
- Genetic mutations and epigenetic changes acquired during carcinogenesis can be detected in stool from DNA shed by colorectal neoplasm
Sampling:
- Individuals collect a full stool sample
- Optimal interval between screening fecal DNA test is every 3 years
Sigmoidoscopy for CRC screening
Testing procedure
Advantages and disadvantages
Testing:
- 60 cm sigmoidoscopy can reach to splenic flexure and can only identify leftsided colonic lesions
- paired with air-contrast barium enema to detect transverse and right-sided colonic lesions
Interval:
- Recommended every 5 years when performed alone or every 10 years if performed along with FOBT or fecal immunochemical test (FIT)
- Follow-up colonoscopy is indicated of multiple or large adenomas (≥ 1.0 cm) and for adenomas with villous histology
Colonoscopy for CRC screening
Testing procedure
Advantages and disadvantages
Testing:
- Definitive test for detection of advanced adenomas and colorectal cancer
- Used for screening, diagnostic and therapeutic purposes
Test procedures
- Aggressive bowel preparation is required
- Recommended to screen every 3-6 months for first 3 year
- Then every 6 months for 2 years
- CEA every 3-6 months
Prognostic determinants of CRC
Local tumour extent (T stage)
- Depth of tumour penetration
Regional nodes (N stage)
- Nodal involvement is the single MOST important prognostic factor in CRC
- 4 or more involved LN predicts a poor survival
- T stage is the single most significant predictor of LN metastasis
o T1 stage = 5%
o T2 stage = 20%
o T3 and 4 stage = > 50%
Lymphovascular invasion
- Perineural invasion
- Grade of differentiation
Molecular factors
- Mismatch repair deficiency (Mutation in DNA mismatch repair (MMR) gene)
- RAS and BRAF mutation
Prognosis based on TNM staging:
5-year survival of colon cancer
* Stage I = 90%
* Stage II = 60 – 80%
* Stage III = 60%
* Stage IV = 10%
Rectal cancer
Difference with colon cancer
DIfferences:
- Transanal access is possible up to 10cm of rectum
- Easier to treat with neoadjuvant RT due to paucity of small bowel
- Confined to pelvis and presence of sphincter impossible to make wide excision
- Proximial to urogenital structures and nerves makes resection more challenging
- More difficult to achieve radial margins
Principles:
- Adequate circumferential margin: distal 2cm margin when TME is performed
- Total mesorectal excision (TME)
- LN clearance with high ligation of arterial pedicle (IMA)
- Sphincter and autonomic nerve preservation
Rectal cancer
Neoadjuvant chemoRT
Advantage and disadvantage
Advatage:
- Downstaging by treating local LN
- Shrinkage to improve resectability and sphincter sparing
- Similar result but significantly less toxicity than post-operative chemotherapy
Disadvantage:
- Over-treatment of early stage tumours
- Impair wound healing
- Increase post-operative complications
- Pelvic fibrosis
Rectal cancer
Treatment in stage 1-4
**Local excision =
Radical resection = Anterior resection/ Abdominal perineal resection (APR)
Stage 1 (T1-2, N0, M0): Local excision/ Radical resection with permenant colestomy
- Radical resection recommended due to high recurrence risk
Stage 2 (T3-4, N0, M0): Neoadjuvant chemoRT + Radical resection
Stage 3 (Any T stage + N1, M0): Neoadjuvant chemoRT + Radical resection
- Advance resection with TME
Stage 4 (Any N and M stage)
- Isloated liver or lung met can be resected for cure
- Palliation for unresectable:
Palliation:
- Endoluminal stent
- Diverting stoma
- Bypass surgery
- Local cauterization or laser ablation for bleeding
Rectal cancer
Surgical treatment selection criteria
Tumor factor:
- Size
- Location from anal verge
- Location from anorectal ring
- LN metastasis
- Invasion in lateral pelvic walls and intra-abdominal organs
Patient factor:
- Firness for surgery
- Pre-surgical anorectal sphincter function
- Pelvic anatomy
Surgeon factors
- Experience
- Hospital equipment
Rectal cancer
Resection margins
Proximal minimum -ve 5cm margin
Distal:
- Try to maximize sphincter preservation
- Failing enough -ve distal margin = convert from sphincter sparing resection to APR
- Minimum -ve distal margin in cancer above distal mesorectal margin = 2cm
- Minimum -ve dital margin in cancer at or below distal mesorectal margin = 1cm
Circumferential radial margin (CRM) = 1cm minimum
Rectal cancers
Surgical techniques
Local excision (no TME)
Transanal endoscopic surgery (TES)
Transanal excision (TAE)
Posterior excision
Radical exicison (with TME)
- Sphincter sparing: Anterior resection (AR)/ Low anterior resection (LAR)
- Non-sphincter sparing: abdominal perineal resection, multivisceral resection/ Pelvic exenteration
TME:
- Trans-abdominally performed with open, laparoscopic, robotic
- Dissect endopelvic fascia for complete removal of rectal mesentery (perirectal areolar tissue)
- Extent: remove lateral and cricumferential margin of mesorectal envelop to 5cm below distal margin for upper rectal tumour, or to pelvic floor for middle or lower rectal tumour
- High ligation of IMA and regional LN dissection
- A/w longer survival, lower recurrence, less bleeding, lower risk of damage to pelvic and presacral nerves compared to blunt dissection
Rectal cancer
Local excision
Indication
Technique
Outcome
Rectal cancer
Radical excision: Anterior resection/ LAR
Indication
Technique
Anastomosis
Indication: ALL of the following criteria has to be met
- Tumours stage = T2 – 4 (Invasive rectal cancer)
- Adequate presurgical anorectal sphincter function
- Able to achieve clear (negative) margins with local excision
Technique:
- Anterior resection: Margin and anastomosis above peritoneal reflection
- Low anterior resection: Margin and anastomosis below peritoneal reflection, Removal of sigmoid colon and rectum to a level where the distal margin is free of cancer + primary colorectal or coloanal anastomosis +/- proximal diverting ostomy or end colostomy (Hartman)
Anastomosis:
- Colonic J-pouch reservoir: J shape neorectal reservoir
- Side-to-end reservoir: T shape coloanal anastomosis
- Transverse coloplasty High risk of leakage
Defunctioning stoma:
- Temporary divertion with loop ileostomy or loop colostomy
- Decreases complication rate and risk of reoperation for anastomotic leakage
- Indicated: Low anastomosis, Anatomosis under tension, Intra-operative leak test positive
Rectal cancer
APR
Indication
Technique
Rectal cancer multivisceral resection
Indication
Technique
Outcome
Guaiac-based fecal occult blood test (gFOBT)
MoA
Specimen
Test performance
Advantage and disadvantage
MoA:
- Guaiac testing of stool samples identifies Hb by the presence of a peroxidase reaction which turns the guaiac-impregnated paper blue
- Guaiac reagents available on marker includes Hemoccult-SENSA (preferred)/ Hemoccult/ Hemoccult-II/ Hemoccult-R
Sample:
- Screening by gFOBT should be performed on 3 consecutive stool specimens
- Vitamin C should be restricted for at least 3 days prior to sampling (cause FN)
- Restrictive diet is NOT necessary as it decreases screening compliance
Test performance
- Hemoccult SENSA: Sensitivity = 64 – 80%; Specificity = 87 – 90%
- Hemoccult II: Sensitivity = 25 – 38%; Specificity = 98 – 99%
Stoma complications
Early complications (Early < 30 days)
o Stomal bleeding
o Stomal necrosis
o Stomal retraction
o Mucocutaneous separation
o Skin irritation and dermatitis (most common in end and loop ileostomy due to highoutput and high alkaline enzymatic effluent)
Late complications (Late > 30 days)
o Parastomal hernia
o Stomal prolapse
o Stomal stenosis
