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Role of high fiber diet in colon carcinoma protection?
High fiber diet has been found to have protective effect by increasing the stool bulk, diluting the toxins, and reducing the colonic transit time and thus reducing exposure time to fecal carcinogensQ
The most frequently mutated tumor suppressor gene in human neoplasia?
p53 (TP53), located on chromosome 17pQ.
Fearon-Vogelstein Adenoma Carcinoma Multistep Model?
- The earliest mutations in the adenoma-carcinoma sequence occur in the APC geneQ.
- The earliest phenotype change present is known as aberrant crypt formationQ
- Most consistent genetic aberrations within these cells are abnormally short proteins known as APC truncations.
- Most APC truncation mutations occur in the mutational cluster region of the gene, an area responsible for beta-catenin bindingQ.
What is Adenomatous Polyposis Coli (APC) Gene?
- Tumor suppressor gene in 5q21Q.
- Its product is 2843 amino acids in length and forms a cytoplasmic complex with GSK-3β (a serine-threonine kinase), β-catenin, and axinQ.
- APC participates in cell cycle control by regulating the intracytoplasmic pool of β-cateninQ.
- APC influences cell cycle proliferation by regulating Wnt expressionQ
Role of cholecystectomy in colon cancer?
- Bile acids can induce hyperproliferation of the intestinal mucosaQ via a number of intracellular mechanisms.
- Cholecystectomy, which alters the enterohepatic cycle of bile acids, has been associated with a moderately increased risk of proximal colon cancersQ.
- Calcium, in fact, binds bile acids and thus may reduce their negative impactQ.
Most common site of colorectal cancer?
Rectum (MC)Q, 38% > Sigmoid colon (2nd MC)Q, 21% > Cecum, 12%
Most common symptom of colon cancer?
Abdominal pain (44%), MCQ > Change in bowel habit (43%)
Role of colonoscopy in colon cancer?
- Colonoscopy is gold standard for diagnosis of colon cancerQ.
- Inspect entire colon to exclude metachronous polyps or cancersQ
- Incidence of a synchronous cancer is about 3%Q.
Contraindication to Liver Resection for Metastatic Colorectal Cancer (Ekberg Criteria)?
- The presence of four metastasis or moreQ
- Extrahepatic diseaseQ
- A resection margin of <1 cmQ
What is Virtual Colonoscopy?
- VC is a medical imaging procedure which uses x-rays and computers to produce two-and three-dimensional images of the colon and rectum and display them on a screen
- VC is performed via CT or with MRIQ
Uses of virtual colonoscopy?
- VC is used to diagnose colonic polyps, diverticulosis and cancerQ.
- VC provides a secondary benefit of revealing diseases or abnormalities outside the colonQ.
Uses of Barium?
- • Barium swallow is used for anatomical disorders of esophagusQ.
- • Barium meal is used for anatomical disorders of stomachQ.
- • Barium meal follow through is used for anatomical disorders of small intestineQ.
- • Barium enema is used for anatomical disorders of large intestineQ.
- • Enteroclysis is also known as small bowel enema, used for small intestineQ.
Most important prognostic factor for colorectal carcinoma?
Stage of the diseaseQ
Single most important independent prognostic factor for colorectal carcinoma?
- LN status
- Tumor size and duration of symptoms has no effect on prognosis of diseaseQ
Modified Duke’s classification of colorectal cancer?
- A - Confined to the bowel wallQ
- B1 - Partially penetrated the muscularis propriaQ
- B2 - Fully penetratedQ the muscularis propria
- C1 - Lymph node invasion without penetration of the entire bowel wallQ
- C2 - Lymph node invasion with penetrationQ of the entire bowel wall
- D - Distant metastasisQ
Management of Metastatic Colorectal Carcinoma?
- At present, only patients who have recurrence of colorectal carcinoma with defined isolated liver, lung, ovarian, or anastomotic metastasis should undergo surgeryQ.
- Prophylactic Bilateral Oophorectomy - Incidence of ovarian cancer with a history of colorectal cancer is five times, so the prevention of primary ovarian cancer in postmenopausal women is considered to be the main benefit.
Management of colon cancer according to staging?
Stages I and II: (T1–3, N0, M0) Localized Colon Carcinoma - Surgical resectionQ
- Stage III: (Tany, N1, M0) Lymph Node Metastasis - Surgical resection+ Adjuvant chemotherapyQ (routinely) • Reference regimen: FOLFOX-IVQ (5-FU, Leucovorin, Oxaliplatin
- Stage IV: (Tany, Nany, M1) Distant Metastasis - MC site of metastasis: Liver >LungQ • Resection (metastasectomy) for isolated, resectable metastasis + adjuvant chemotherapyQ • Palliation for unresectable disease
Indications of adjuvant chemotherapy in Stage II?
- 1. Insufficient lymph node samplingQ (<12 nodes resected with the specimen)
- 2. Perivascular invasionQ
- 3. Poorly differentiated histologyQ
- 4. Bowel obstruction or perforationQ
Chemotherapy in CA Colon?
- FOLFOX-IVQ (5-FU, Leucovorin, Oxaliplatin) is the reference regimen with infusional 5-FU
- • Bevacizumab, cetuximab and panitumumab should also not be used in the adjuvant setting, as they add toxicity and expense, and do not add benefit.
- • Irinotecan, bevacizumab and cetuximab are used for systemic metastatic disease or stage IVQ
Half-life of CEA?
- 7-14 daysQ
- CEA is most sensitive for detection of retroperitoneal and hepatic metastasesQ
Rationale of follow up colonoscopy?
- Not to define recurrent cancer; the major rationale is to define synchronous or metachronous bowel tumors, usually polyps.
- Colonoscopy is recommended at 1 year after resectionQ, and every 3 years thereafter