Colon Cancer Flashcards
T1
invades submucosa
T2
invades muscular propria
Tis
intramucosal cancer cells, does not breach muscular mucosal
T3
invades subserosa or into nonperitonealised pericolic or perirectal tissue
T4a
penetrates surface of visceral peritoneum
T4b
directly invades other organs
N1c
tumor deposits in the subserosa or non-peritonealized /perirectal soft tissue WITHOUT regional lymph node metastasis
Isolated tumor cells
20 cells within subcaosular or marginal sinus of lymph node
Micrometastases
cluster of 20 or more cells OR metastases measuring 0.2-2mm in diameter
N1a
1 regional lymph nodes
N1b
2-3 regional lymph nodes
N2a
4-6 regional lymph nodes
N2b
>7 regional lymph nodes
CEA
- oncofetal antigen
- first pass effect of liver
- ~40-50% of CRC raised
- Prognostic: >20 is poorer prognosis
- Surveillance
Adenoma-carcinoma sequence
1) APC gene mutation
2) Activating K-ras oncogene
3) Inactivate p53 tumor suppressor gene
Molecular pathways for colorectal tumorigenesis
1) Chromosomal instability (APC) pathway
2) Mismatch repair pathway
3) Serrated /Hypermethylation phenotype (CIMP+) pathway
Chromosomal instability (APC) pathway
- can be inherited (FAP) or sporadic
- gross chromosomal abnormalities (deletions, insertions, loss of heterozygosity)
Oncogenes involved in sporadic CRC
RAS
SRC
MYC
HER2
RAS oncogene
- point mutations
- mutation restyle in continuous growth stimulation
- 50% sporadic CRCs
- 50% colonic adenoma > 1cm
3 subtypes HRAS, KRAS, NRAS
Tumor suppressor genes associated with CRC
APC
TP53
Chromosome 18q: DCC, SMAD4, SMAD2
TGF-beta signalling
BRCA1 and BRCA2
Mismatch repair genes
-responsible for correcting nucleotide base mispairings/ small insertions/deltions during DNA replication
hMSH
hMLH1, 3
hPMS1,2
hMSH6
KRAS
- Encodes a small G protein on EGFR pathway
- Wild type RAS = normal
Colonoscopy documentation
Extent of examination
Photodocumentation of landmarks
Bowel prep quality
Location, size, morphology of lesions
Removal technique and completeness
Tattoo placement
Metachronous tumor
Tumor detected more than 6 months after management of index tumor
SIGGAR trial 2013
lower detection rate AND miss rate of Barium enema compared to CTC
Pros and cons of PEG
Polyethylene glycol solution
Pros:
-minimal volumen shift
-minimal electrolyte disturbance
Cons:
-requires compliance
-risk of aspiration
Pros and cons of sodium phosphate agent
Pros:
-small volume and quantity
-better tolerance
-better compliance
Cons:
-C/I in renal impairment due to phosphate content
-risk of volume shift
-risk of electrolyte disturbance
Rationale to forgo bowel prep before elective colonoic surgery
- most anastomotic leaks due to technical error and biological failure
- Cochraine 2011 studies showed DID NOT reduce complication rate
When may bowel prep be considered in elective surgery
-proximal stoma planned
(prevents stagnant stool remaining in left side of coon
-easier bowel handling
-facilitate on-table colonoscopy
Peri-operative blood transfusion in CRC surgery
- immunosuppressive
- increase wound infection
- increase intra-abdominal collection
- increase recurrence (Cochrane Rev 2011)
TRIM
Transfusion related immune modulation
immune suppression leading to tumor proliferation and invasion
Evidence for MDT approach
- reduce rate of positive CRM for rectal cancer
- increase rates of adjuvant therapy for colon cancer
- increases rates of metastasis surgery for patient ins stage 4 disease
Right hemicolectomy
- Definition
- Vascular supply
- Indication (tumor location)
- Removal of 10cm TI, AC HF and proximal 1/3 TC
- ileocolic, right, right branch of middle colic
- Cecal, AC cancer
Extended right hemicolectomy
- Definition
- Vascular supply
- Indication (tumor location)
- removal of 10cm TI, AC, TC, SF
- ileocolic, right, middle +/- ascending branch of left colic
- HF, proximal, mid transverse colon
Left hemicolectomy
- Definition
- Vascular supply
- Indication (tumor location)
- left colon
- Ligation of IMA at origin
- splenic flexure, descending colon, sigmoid colon
Extended left hemi-colectomy
- Definition
- Vascular supply
- Indication (tumor location)
- distal 1/3 of TC, colorectal junction
- left branch of middle colic, IMA
- splenic flexure tumor
CA splenic flexure.
How to decide between extended right and left hemicolectomy?
- Oncological clearance (anatomy of blood supply to splenic flexure and lymph nodes involved)
- Technical aspect (tension free and good blood supply to anasomosis
- Caecum and proximal colon viability
Surgical options for Splenic Flexure Cancer
Extended right hemicolectomy
Extended left hemicolectomy
Segmental splenic flexure resection
Segmental splenic flexure resection
left branch of middle colic and left colic vessels
Variation in supply of splenic flexure artery
89% by left colic
11% by SMA
Missing middle colic 22%
5 year survival rate in colon cancer for each stage
Stage 1: 90%
Stage 2: 70%
Stage 3: 50%
Stage 4: 10%
Left segmental colectomy
- Definition
- Vascular supply
- Indication (tumor location)
- Resection of descending colon
- Left colic artery
- Descending colon tumor
Indication for adjuvant chemotherapy in colon cancer
- Stage III
- Stage II with high risk features controversial, no definite evidence
Evidence for addition of oxaliplatin to adjuvant chemotherapy in colon
MOSAIC
NSABP C07
XELOXA
Adjuvant chemotherapy regimen for colon cancer
Oxaliplatin based regimen:
- XELOX
- FOLFOX
- FLOX
For 6 months after recovery from surgery
Complications of large bowel operation
- Early
- Anastomotic leak
- Accidental injury to other organs
- Infection/ sepsis (wound, intra-abdominal)
- Ileus
- Late
- Diarrhea
- Impotence
- Urinary incontinence
- Adhesive I/O
High risk features in Stage II colon
- Poorly differentiated
- Serosal involvement (T4)
- Lymphovascular permeation
- Margin involved
- Extramural vascular invasion
- Perineural invasion
- Obstructed/perforated tumor
- Fewer than 12 LN
- Markedly elevated CEA
How to decide for adjuvant chemo in Stage II colon cancer?
Adjuvant! Online tool
weights potential benefit with life expectancy, toxicity and risk
