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Colon Cancer
Gastroenterology
| Question | Answer |
|---|---|
| Colon cancer risk: | doubles each decade after 40 yo; M>F; 90% occur after 50; sig higher risk if 1st-degree relative with colon ca |
| Colon cancer Genl RFs | Age; Personal hx colon polyps or ca; FH; inherited syndromes; T2DM; IBD |
| Colon cancer lifestyle RFs | Diet (red meat); physical inactivity; obesity; smoking; heavy alcohol use |
| 2 types of dx criteria for HNPCC | Amsterdam; Bethesda |
| S/S colon cancer | Rectal bleeding; Fe def anemia; Fatigue / wt loss; obstruction (left sided tumors); change in stool quality/caliber; abdominal mass or abd pain |
| Colon cancer: most common metastases are to: | liver, then lung (colon); liver or lung (rectal ca) |
| Colon cancer: gold standard of dx eval: | colonoscopy |
| Colon cancer: other dx eval | CT with contrast abd/pelvis (for staging). CXR. Needle bx of suspected mets. PET scan only for suspected mets dz |
| Colon cancer: labs | CBC, chemistry; may check CEA, but not for dx (help w/staging) |
| Cancer stage is determined from: | PE, biopsy, imaging, lymph node dissection |
| Layers of colon wall | Mucosa; muscularis mucosa; submucosa; muscularis propia; subserosa/serosa |
| Types of ablation of mets | Radiofrequency Ablation; Ethanol ablation; Cryosurgery; Hepatic artery embolization |
| Goal of chemo: | Eradicate micrometastasis to increase likelihood of cure; none for stage 0 or I; resected stage II: poss modest survival benefit but not routinely recommended |
| Indications for radiation tx in colorectal cancer | not typically used for colon cancer. Used for rectal cancer |
| Screening: stool Tests: | primarily detect cancer; Guaiac FOBT & immunochemical-based FIT; Stool DNA (sDNA) |
| Screening: Structural Exams: | Detect cancer and polyps; Colonoscopy; CT colonography; Flexible Sigmoidoscopy; Double-contrast barium enema (uncommon) |
| Best mortality data for CRC screening: | Guiac FOBT |
| Never screen for colon ca with: | DRE |
| Positive FOBT should always be followed by: | colonoscopy (and no more FOBTs needed) |
| Negative FOBT tests should be: | repeated annually |
| Flexible Sigmoidoscopy procedure description | Examines left colon; some bowel prep needed; can be performed w/o sedation in Dr’s office. 5-year interval between exams |
| Patients w/ adenomas found on flex sig should: | have a colonoscopy |
| Colonoscopy: procedure description | Direct inspection of entire colon with sedation (usu conscious); thorough bowel prep required |
| Colonoscopy false negative rates | 6-12% miss rates for large adenomas; 5% miss rates for cancer |
| Most common serious complication of colonoscopy | bleeding post-polypectomy; Perforation = 1/1000 and increases with age and diverticular disease |
| Colon cancer screening | FOBT at age 50-75 yrs (alt: colonoscopy or sigmoidoscopy). USPSTF: no screen for >75 y.o. |
| Colon cancer surveillance | once ca/adenomatous polyps are detected, occurs at shorter intervals (usually repeat colonoscopy in 3-5 years); If FH CRC: every 5 yr; IBD: yearly once disease present for more than 15 yr |
| Colon polyps (types) | adenomatous (poss pre-malig: req shorter surveillance colonoscopy interval); hyperplastic (not considered pre-malig) |
| CT colonography | No sedation; req bowel prep; pos result req f/u colonoscopy |
| Colon polyps: more likely to be malignant if: | sessile, >1cm, villous |
| Colon polyps: less likely to be malignant if: | pedunculated, <1cm, tubular |
| If 2 first-degree relatives have CRC or 1 relative with colon ca or adenomatous polyps: | Screen at 40 y.o. (or 10 yrs <earliest family dx) |
| Colon ca: most common metastases are to: | liver, then lung (colon); liver or lung (rectal ca) |