EXAM #3: COLORECTAL CANCER Flashcards
What are the landmarks for the colon?
1) Tenia coli
2) Transition from colon to rectum where the Tenia coli “splay”
What are the major arteries that branch from the SMA to the colon?
SMA supplies proximal 2/3 of the colon–branches include:
1) Ileocolic
2) Right colic
3) Middle colic
What are the major arteries that branch from the IMA to the colon?
IMA supplies the distal 1/3 of the colin–branches include:
1) Left colic
2) Sigmoidal branches
3) Superior rectal
What arteries supply the rectum? Where do these arteries branch from?
1) Superior rectal from the IMA
2) Middle and inferior rectal from the internal iliac arteries
Review the layers of the GI mucosa.
1) Mucosa
- Epithelium
- Lamina propria
- Musclaris mucosa
2) Submucosa
3) Muscularis Propria
4) Serosa
How prevalent is colon cancer?
3rd most common cancer
List the risk factors for colon cancer.
1) Family history
2) IBD
3) Smoking
4) Alcohol
5) Obesity
6) Inactivity
7) Diet rich in red meat and animal fat
What factors are protective against colon cancer?
1) Hormone Replacement Therapy
2) NSAIDs
3) Diet rich in fiber, fruits, and veggies
Outline the Adenoma-Carcinoma Sequence.
1) APC= early adenoma
2) K-RAS= intermediate adenoma
3) DCC= late adenoma
4) p53= carcinoma
*Note that this normally takes roughly 10 years.
How can adenomatous polyps be removed via colonoscopy?
Snare excision
What are the four most common etiologies of colon cancer?
1) Sporadic
2) Non-syndromic familial colorectal cancer
3) FAP
4) HNPCC or Lynch Syndrome
What mutation is associated with FAP?
Autosomal dominant APC mutation
Chromosome 5
What is the clinical manifestation of FAP?
1,000 of adenomatous polyps
- Early onset
- WILL get colon cancer
What is the treatment for FAP?
Total colectomy
What genetic defect is seen in HNPCC?
Defects in DNA mismatch repair genes
What are the clinical manifestations of HNPCC?
- 100s of polyps
- Accelerated progression to colon cancer
*Not a 100% progression to cancer like APC.
What cancers are associated with HNPCC in addition to colon cancer?
Endometrial
Ovarian
What is the treatment for HNPCC?
Colectomy
What sign is associated with advanced polyps?
Fecal occult blood test
What are the three major screening modalities for colorectal cancer?
1) Colonoscopy*
2) Flexilble sigoidoscopy
3) FOBT (Fecal Occult Blood Test)
*Gold standard
What imaging modalities are used to screen for colorectal cancer?
1) Double contrast barium enema
2) CT Colongraphy
What is the difference between colonscopy and flexible sigmoidoscopy?
Flexible sigmoidoscopy isn’t as long (will only reach the splenic flexure)
*Note that you develop more polyps in the distal colon/rectum, which is why this is used as a good alternative to colonoscopy
What is the drawback to the fecal occult blood tests?
Detects more ADVANCED polyps or cancer
What are the drawbacks to double contrast barium enemas?
1) Still requires bowel prep
2) Give rectal air and contrast
3) Only detects advanced polyps
Plus, if its positive, you still have to get a colonoscopy.
What are the drawbacks to CT Colonography?
Same as barium enema.
What are the screening recommendations for colorectal cancer?
1) Colonoscopy every 10 years
2) Flexible sigmoidoscopy every 5 years AND FOBT every 3 years
3) FOBT every year
When do you start screening?
If AVERAGE risk, start at 50 y/o
*Average= no family history or personal history of polyps/cancer
What gives a patient a positive family history of colon cancer?
1) First degree relative with hx at less than 60
2) 2x first degree at ANY age
3) Second degree relative less than 50
When do you start screening for patients with a family history of colon cancer?
40 y/o AND repeat every 5 years
What are the screening recommendations for colon cancer in patients with IBD?
1) Start colonoscopy 8-10 years after onset of sx.
2) Collect 4x random biopsies every 10cm (total of 30+)
*Repeat every 1-2 years
When do you start screening for colon cancer in HNPCC?
Age 20-25 y/o
*Repeat every 1-2 years
What are the screening recommendations for FAP?
Age 10-12 y/o
*Repeat every 1-2 years
What is the most common cause of colon obstruction in adults?
Colorectal cancer
What symptoms are associated with colorectal cancer?
- Vague abdominal pain
- Change in bowel habits e.g. pencil-thin stool
- GI Bleeding
For a person that presents with symptoms suggestive of colon cancer, what imaging should be ordered?
1) KUB
2) CT abdomen and pelvis with IV and enteral contrast
3) Colonoscopy or Proctoscopy
- TATTOO the lesion!
What is the serum tumor marker for colon cancer? How is this used?
CEA= carcinoembryonic antigen
*Clinically this is used for surveillance s/p resection
What is the TNM classification system?
T= invasion depth of Tumor
N= extent of regional lymph Node involvement
M= Metastasis
Outline the different T-stages of tumors.
Tis= intraepithelial T1= Submucosa T2= Muscularis propria T3= Pericolorectal tissue T4a= Penetrates peritoneum T4b= invading adjacent organs
Outline the N-stages.
N0= no nodes N1= 1-3 regional nodes N2= 4+ nodes
How many nodes need to be examined for adequate staging?
At least 15 nodes
Outline the M-stages.
M0= no mets M1= distant mets
What resection margins do you need to have in the treatment of colon cancer?
5cm
1-2cm in the rectum
What determines your resection margin in the treatment of colon cancer?
The resected artery
*All bowel associated with artery needs to be removed
What is a Low Anterior Resection (LAR)?
Rectosigmoid resection below the peritoneal reflection
*This procedure preserves the anal sphincter and opening
What is an Abdominal Perineal Resection (APR)?
Rectosigmoid resection including:
- Anal sphincters
- Anal opening
When does colon cancer require the addition of chemotherapy to surgical resection?
1) Any nodal disease
2) Some T3 and any T4+ disease
What colon cancer mets are treated with resection?
Liver and lung metastases
What colon cancers are treated primary with chemotherapy and secondarily with palliative resection?
1) Bleeding
2) Obstruction
3) Perforation
What is the treatment for Tis and T1 rectal cancer?
Transanal excision
What is the treatment for T2 rectal cancer?
Surgical resection
What is the treatment for T3, T4, or N+ rectal cancer?
1) Neoadjuvant (i.e. begin with) chemoradiation
2) Surgical resection
After surgical resection, what are the recommendations for surveillance?
1) H and P every 3-6 months for 5 years
2) CEA same
3) CT annually for 5 years
