Colorectal Cancer - Fich Flashcards
Sequence from adenoma to carcinoma
Which polypectomy techniques are used and when?
Hot/cold biopsy if polyp is very small
Hot/cold snare-common. Uses electricity so no bleeding.
Saline elevation with a snare: for more flat sessile polyps, raise mucosa first.
Laser and piecemeal snare-not used today.
Family Associated Polyposis Syndrome
Genetic defect characterized by deletion of APC genes (protector gene)
Hundreds of polyps in colon of young individual
Usually begin developing at age 12-14
Probability of carcinoma is 95-100% because of the number of polyps
Preventative colectomy recommended
Make up 1% of all colon cancers
Hereditary Nonpolyposis Colon Cancer (HNPCC)
aka Lynch Syndrome
Epidemiology, diagnosis, properties
5% of colorectal cancer cases
Familial-Autosomal dominant
Early onset of multiple primary cancers.
Right colon predominance
Few or no adenomas (no process of polyps turning into carcinomas)-carcinoma arises from nondysplastic or small polyps directly
Frequent endometrial cancer as well
Microsattelite instability: Most common mismatch repair genes: hMSH2 and hMLH1
Diagnosis: Amsterdam Criteria:
3 or more relatives with colorectal, endometrial, small bowel, ureter, or renal pelvis cancer
At least 2 successive generations affected
At least 1 tumor diagnosed before the age of 50 years
FAP has been excluded
Bethesda criteria includes suspicion in a larger population and then does microsatellite genetic test
Colonoscopy recommended starting at age 20-25 every 2 years.
50% lifetime risk of colorectal cancer.
Symptoms and findings in varying time course of colorectal cancer
Early: No sympoms, no finds or occult blood (especialy on the right side)
Mid: Rectal bleeding, change in bowel habit. Rectal mass, blood in stool (more in tumor on left side or near rectum, don’t assume they are hemorrhoids).
Late: Fatigue, pallor, abdominal pain. Weight loss (cachexia), abdominal mass, hepatomegaly, bowel obstruction (do emergency colonoscopy with temporary stent, avoids extra surgery of rerouting bowel and removing tumor).
Staging prognosis, definition and treatment
Stage 0: TIS: in situ. Surgery alone is enough
I: T1 and T2: submucosa and muscularis propria invaded.
II: T3 and T4: serosa and adjacent organs invaded.
Stage III: Lymph node involvement. Chemo and surgery together.
Stage IV: metastasis. No point in surgery, do palliative chemo.
Primary prevention of colorectal cancer
Exercise (decreases insulin and IGF1 receptors)
Low fat diet rich in fruits and vegetables
Fiber??
Chemoprophylaxis:
NSAIDs (1 baby aspirin per day)
Calcium
Estrogen
Folate
Selenium
Screening methods
Annual fecal occult blood test (FOBT)
Push from epidemiologists, easy test, cheap. Problems: can miss CRC and give false sense of security, doesn’t detect polyps at early stage. Must do annually (30% reduction in mortality), sporadic doesn’t as much.
Flexible sigmoidoscopy every 5 years
Only left part of colon, most polyps on this side but not all.
Annual FOBT + flexible sigmoidoscopy every 5 years
Increase chances of detecting early tumors.
Colonoscopy every 10 years
Current recommendation after age 50 for average risk. For family history: start colonoscopies at age 40 or 10 years before.
Once-in-a-lifetime colonoscopy- age 55-60
Double contrast barium enema every 5 years
Virtual colonoscopy
CT Scan. Doesn’t recognize polyps <1cm in size.
Videocapsule
Usually for small bowel, but no radiation.
Stool testing for DNA
For all methods other than colonoscopy, if positive need to prep again for regular colonoscopy.
