Colon Cancer Flashcards
What is the flexure of the right colon?
Hepatic flexure
What is the flexure on the left side of the colon?
Splenic flexure
What are the folds that help hold stool in the rectum?
Transverse rectal folds
What are the branches of the SMA?
ileocolic
Right colic
Middle colic
What are the branches of the IMA?
Left colic
Sigmoidal
Rectal
What is the blood supply to the superior part of the rectum? What is this a branch of?
Superior hemorrhoidal
Branch of the IMA
What is the blood supply to the inferior part o the rectum? What are these branches of?
Middle rectal
Inferior rectal
Both branches of the internal iliac
What are the four histological layers of the colon?
Mucosa
Submucosa
Muscularis propria
Serosa
What are the three big CAs? (as far as incidence, in order)
Prostate/breast
Lung
Colon
What are the risk factors for the development of colon CA?
IBDs
Obesity
What diet is a risk factor for colon cancer?
Red meats and animal fats
What are the three protective factors for colon cancer?
Hormone replacement therapy
NSAID use
Fiberous diet
What are the four DNA proteins that are implicated in colon CA?
APC
KRAS
DCC
p53
What is the order of genetic mutations of the adenoma-carcinoma sequence?
APC
KRAS
DCC
p53
How long does it take for the adenoma-carcinoma sequence to develop?
10 years
What changes with APC gene mutation?
Dysplastic aberrant crypt foci
What changes with KRAS mutation?
Intermediate adenoma
What happens with DCC mutation?
Late adenoma
What happens with -53 mutation?
Carcinoma development
Most etiologies of colon cancer are from what?
sporadic (80%)
What is the genetic mutation in familial adenomatous polyposis? How does this present? What is the treatment for this?
APC gene mutation on chromosome 5q
Tons o’ polyps early on
Total colectomy
What is Hereditary Non-Polyposis Colon Cancer (HNPCC/lynch syndrome)? Presentation? Treatment?
Mismatch defect in repairing chromosomes
Hundreds of polyps
Total colectomy
What are the ssx of early poylps? Late?
asymptomatic early
Maybe positive fecal occult blood test for late
What are the three major screening modalities for colon CA screening?
Colonoscopy
Flexible sigmoidoscopy
FOBT
What are the two radiological modalities of screening for colon cancer?
Double contract Ba enema
CT colonography
What is the gold standard for colon CA screening?
Colonoscopy
What is flexible sigmoidoscopy? Advantages/disadvantages?
similar to colonoscopy, but only reaches the splenic flexure
Do not have to prep as much and less sedation
Cannot excise polyps***
What does stool guaiac blood test assess for?
Peroxidase activity
What does the fecal immunochemical test assess for?
Antibody test
What is a double contrast Ba enema?
Rectal air and contrast instilled and visualize the colon wall
Requires cathartic bowel prep
What is a CT colonography?
Rectal air and contrast instilled, as well as cathartic bowel prep
How often do you repeat colonoscopies? Flexible sigmoidoscopies? FOBTs?
Colonoscopy = 10 yrs
Flexible sigmoid = 5 yrs + FOBT 3 years
FOBT = every 1-3 years
What are the three characteristics of “average risk” for colon CA?
Asymptomatic
No family h/o CA
No personal h/o polyps/CA
What are the three characteristics of the higher risk pt that should start colonoscopies at age 40, and repeat every 5 years?
- First degree relative less than 60 yo
- 2x first degree relatives any age
- Second degree relative age less than 50
What should colonoscopies begin with IBDs? What is different about these (frequency, what is done)?
8-10 years, 1-2 years
must collect 4x random biopsies
When should colonoscopies begin with lynch syndrome? Frequency?
20-25, repeat 1-2 years
When should colonoscopies being in pts with FAP/APC mutation? Frequency? When should a total colectomy be performed?
10-12 yo
Repeat 1-2 years
Colectomy as soon as polyps are seen
What are the ssx of colon CA (if any)? (5)
- Vague abdominal pain
- Change in bowel habits
- Bleeding
- Obstruction
- Perforation
Where do colon CAs usually metastasize to?
inguinal lymph nodes
What is the dye that is used to tattooing the site of a polypectomy?
Methylene blue
During a proctoscopy, from where do you measure from to the polyp?
Sphincter
What is the serum marker for colon CA? What is this used for?
CEA
Used as a surveillance marker
What is the purpose of doing a CT/PET scan after biopsy of a malignant polyp?
Check for mets
T1 tumor = ?
Muscularis mucosa into submucosa
T2 tumor = ?
INvades muscularis propria
T3 tumor = ?
INvades pericolorectal tissues
T4a tumor = ?
Penetrates peritoneum
T4b tumor = ?
Invades adjacent organs
Tis tumor = ?
Intraepithelial
N0 = ?
No regional node mets
N1 = ?
1-3 mets in nodes
N2 = ?
4+ nodes
How many nodes need to be examined for adequate node staging?
15 nodes
Where are nodes collected from for staging colon CA?
Visceral mesentery
What are the M stages?
M0 = no mets M1 = distant mets
What are the margins needed for colon resections? How is this determined?
5 cm
Based on blood supply–All bowel supplied by the resected vessel must be removed
What is involved in a colectomy?
Resected colon with associated mesentery
What is involved in a low anterior resection (LAR)?
Rectosigmoid resection extending below the peritoneal reflection
What is involved in an abdominal perineal resection?
Rectosigmoid resection including anal sphincters, anal opening, and associated mesorectum
What is the treatment for T1, T2, or T3 colon cancers?
Surgical resection is enough
What is the treatment for T3, T4 colon cancers?
Surgical resection with chemo
N1 or N2 colon cancers treatment = ?
Surgical resection + chemo
What is done with mets from colon CA to the live or other nearby organs? Why is this different than other CAs?
Resect them–provide better outcome. Others “cat’s out of the bag”
What are the three palliative resection cases for colon CA?
Bleeding
Perforation
Obstruction
What is the treatment for Tis or T1 rectal CA?
Transanal excision
What is the treatment for T2 rectal CA?
Surgical resection
What is the treatment for T3, T4, or N+ rectal cancer?
Neoadjuvant chemoradiation + surgical resection
What are the three surveillance measures for rectal CA? Frequency?
H&P ever 3-6 yrs
CEA “ “
Ct x5 years
