Colon Cancer Flashcards
Incidence of colon cancer?
3rd m/c cancer
Affects women slightly more than men
72,600 cases (11%) men #3
75,700 cases (12%) women #3
Pathophysiology of colon cancer
Arises from “benign” adenomatous polyps (80% of time) in normal epithelium -> early adenoma -> intermediate adenoma -> late adenoma -> carcinoma.
Risk factors for colon cancer
- Age
- High fat
- Colonic Polyps
- PMH
- FHx
- UC or Crohn’s disease
Symptoms of colon cancer
- Changes in bowel habits: diarrhea or constipation, color of stool (red, maroon or dark), -narrow or thin stool
- Abdominal discomfort (with eating)
- Weight loss
- Anemia (microcytic)
Dark maroon, continuous bleeding
Right colon cancer, blood acted on by bacteria
Maroon blood
Transverse colon
Bright red blood
Rectal bleed
-Rectal cancer until proven otherwise!
Chance of polyp greater than 1 cm to become malignant after 20 years?
25%
Percentage of colon cancer associated with FAP or HNPCC?
6%
Screening for colon cancer?
Average risk -FOBT + Flex sig q5yr -DCBE q5yr -Colonoscopy q10yr High risk -for large (1cm+) or multiple adenomatous polyps removed: Colonoscopy q3yrs. DCBE + Flex sig as alternative -Family Hx: normal but start at 40yo -Genetic syndromes: Annual flex sig at puberty if possible,
Of hereditary “germline mutations” what is the distribution of diseases?
90% Hereditary non-polyposis colon cancer (HNPCC) “Lynch syndrome”
10% FAP (Familial adenomatous polyposis)
Pathophysiology of FAP
It is a Gene defect: APC gene mutation.
- APC is tumor suppressor gene
- beta-catenin and c-myc downstream targets
- AD inheritance
Presentation of FAP
“carpet of polyps” in colon, teens or early 20s.
Rx FAP
Total colectomy
Gardener’s syndrome
FAP with prominent benign extra-colonic manifestations (osteomas, cutaneous desmoids and fibromas)
Turcot’s syndrome
Colorectal cancer with CNS malignancies (medulloblastoma, astrocytomas, ependymomas (FAP) or glioblastoma (HNPCC)
FAP associated cancers
Brain (medulloblastoma) hepatoblastoma Pancreas thyroid Biliary tree Gastroduodenal Periampullary Hepatoblastoma
Gene defect in HNPCC
mutation in mismatch repair genes: hMLH1 in 95% of cases
Inheritance of HNPCC
AD
HNPCC associated cancers
colorectal endometrium ovary ureter pancreas brain - glioblastoma
HNPCC-associated non-cancerous lesions
- cafe au lait spots
- sebaceous gland adenomas (muir-torre syndrome)
- keratoacanthomas
Patient with known FAP had colectomy 5 years ago. Does he need follow-up? What should you tell his family?
upper endoscopy with attention to duodenal and papillary area
Family should undergo genetic testing for mutated APC at age 12, adults full colonoscopy
Children <5 yearly alpha-feto-protein levels and liver imaging to look for hepatoblastoma
Amsterdam II Criteria for diagnosis of HNPCC?
- 3+ relatives with HNPCC
- Colon cancer involves 2 GENERATIONS
- one diagnosed <50 years of age
Screening of individual with family member diagnosed with CRC <55 years?
colonoscopy 5 years earlier than earliest cancer in the family
M/C causes of rectal bleeding in 60+ year old male
Hemorrhoids > Colon cancer > AVM
Palpation of sister mary joseph’s node
implies metastatic cancer
3 most specific signs for CRC?
Rectal mass = pathognomonic
Rectal bleeding
Anemia
Pre-op labs before CRC surgery?
CBC
Serum chemistry profile - serum electrolytes, BUN/creatinine
PT/PTT - bleeding? but best screening is past history of bleeding
Urine analysis - infx increases risk of surgery
Liver chemistries - check for mets
CEA - establish baseline for future post-op surveillance testing
Postoperative surveillance labs?
CEA - most cost effective, 64% recurrences detected by first CEA
LFTs poor sensitivity and specificity, not recommended by ASCO
What is CEA?
Carcinoembryonic antigen - glycoprotein expressed in the glycocalyx of gastro-intestinal mucosal cells esp in colon and rectum.
Normal levels of CEA?
2.5-3.0 ng/mL in nonsmokers
5ng/mL in smokers
How often is CEA elevated if patient has metastatic colorectal cancer?
85% of time. Not specific marker - Elevated in lung, breast, other GI esophageal, gastric, pancreatic malignancies.
Is CEA used for routine screening?
No, sensitivity is 40%, not specific. Elevated levels associated with obesity, older age, smoking cigarettes, alcohol. 250 false positives for every one positive. Used as prognostic indicator for recurrence.
Why is SMA-7 ordered preop?
Basic metabolic panel to assess electrolyte abnormalities in hypertensive patient who may be using a diuretic.
Is neoadjuvant chemoradiation therapy indicated for CRC?
Colon - Generally not indicated.
Rectal - very useful in some patients with locally advanced rectal cancer: Decrease recurrence in pelvis, shrink tumor, facilitates negative margin resection
Margins acceptable in rectal cancer resection?
5 cm proximally
distal margin of at least 2 cm
full resection of lymphovascular pedicle to include at least 12 lymph nodes
Describe the series of NSIM (assuming each step is positive for cancer or suspected cancer) for patient with 3x2 cm fixed mass on posterior wall of rectum 4 cm above levator muscles.
Anoscopy -> Biopsy -> Colonoscopy -> CT Scan -> Surgery or neoadjuvant
Screening for patients with FAP
Flex sig each year at puberty
Screening for patients with HNPCC
flex sig at 25
Workup for colon cancer
CEA, CXR, abdominal, pelvic CT, CBC, platelets, chem,
Gene in FAP
APC gene, tumor suppressor, AD with 90% penetrance, 5q21
Gene in HNPCC
DNA mismatch repair genes, 80% lifetime risk.
Cancers associated with HNPCC
Colon
Endometrial - 40%
Stomach - 15%
Ovarian 10%
