Colon Cancer Flashcards by Oliver Fischer

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

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Pathophysiology of colon cancer

Arises from “benign” adenomatous polyps (80% of time) in normal epithelium -> early adenoma -> intermediate adenoma -> late adenoma -> carcinoma.

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Risk factors for colon cancer

Age
High fat
Colonic Polyps
PMH
FHx
UC or Crohn’s disease

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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)

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Dark maroon, continuous bleeding

Right colon cancer, blood acted on by bacteria

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Maroon blood

Transverse colon

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Bright red blood

Rectal bleed

-Rectal cancer until proven otherwise!

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Chance of polyp greater than 1 cm to become malignant after 20 years?

25%

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Percentage of colon cancer associated with FAP or HNPCC?

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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,

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Of hereditary “germline mutations” what is the distribution of diseases?

90% Hereditary non-polyposis colon cancer (HNPCC) “Lynch syndrome”
10% FAP (Familial adenomatous polyposis)

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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

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Presentation of FAP

“carpet of polyps” in colon, teens or early 20s.

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Rx FAP

Total colectomy

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Gardener’s syndrome

FAP with prominent benign extra-colonic manifestations (osteomas, cutaneous desmoids and fibromas)

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Turcot’s syndrome

Colorectal cancer with CNS malignancies (medulloblastoma, astrocytomas, ependymomas (FAP) or glioblastoma (HNPCC)

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FAP associated cancers

Brain (medulloblastoma)
hepatoblastoma
Pancreas
thyroid
Biliary tree
Gastroduodenal
Periampullary
Hepatoblastoma

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Gene defect in HNPCC

mutation in mismatch repair genes: hMLH1 in 95% of cases

Inheritance of HNPCC

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%