Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
27 Cards in this Set
- Front
- Back
|
Risk Factors for Colon Cancer
|
age
90% of cases occur after age 50 rare before age 40 family history up to 25% of cases inflammatory bowel disease maybe: red meat, alcohol, tobacco, diabetes, obesity maybe protective: ASA-NSAID, fruits-vegetables, fiber |
|
|
What age is important to begin screening
|
50
|
|
|
Predisposing conditions
|
Family Hx most important
|
|
|
Death from colon cancer and race
|
black>white>hispanic>asian
|
|
|
K-ras
|
most frequent mutation of the ras oncogene in CRC
this mutation effectively leaves the growth switch ON |
|
|
Adenomatous Polyposis Coli (APC) gene
|
the most important tumor suppressor gene in CRC
mutation of this gene leaves cell growth unchecked |
|
|
p53 gene
|
“the guardian of the genome” produces a DNA-binding protein that activates transcription of growth inhibitory genes
mutation of this tumor suppressor gene can result in uncontrolled cell division |
|
|
Sporadic Colon Cancer
|
result from stepwise occurence of multiple somatic mutations
APC – MMR – K-ras – p53 80, 15, 50, 70% respectively |
|
|
Inherited Colon Cancers
|
result from single germline mutations
FAP: APC gene HNPCC: MMR gene |
|
|
Colon Cancer Pathogenesis
|
APC, MMR, KRAS, KRAS, p53
|
|
|
The Adenoma-carcinoma sequence
|
takes 5-10yrs
starts with normal colon-small polyp, large polyp, high grade dysplasia, cancer |
|
|
Familial Adenomatous Polyposis (FAP)
|
Variant forms:
Gardner’s Syndrome Turcot’s Syndrome autosomal dominant germline mutation of the APC gene located on chromosome 5q21-q22 1/3 of cases represent new mutations (no family history) represents less than 1% of the total CRC risk clinical manifestations: more than 100 colorectal polyps polyps begin to develop in 2nd decade average age of colon cancer diagnosis is age 39 compared with age 65 in the average US population 100% will have colon cancer by age 45 duodenal ampullary carcinoma |
|
|
Hereditary Nonpolyposis Colorectal Cancer
|
also called:
HNPCC Lynch Syndrome autosomal dominant germline mutations in DNA mismatch repair (MMR) genes more rapid adenoma-carcinoma sequence average age of colon cancer diagnosis is age 48 60% lifetime risk of colon cancer predominance for the right side of the colon synchronous (cancers in diff parts of colon at same time)and metachronous (colon cancers diff times) cancers are common extra-colonic tumors: uterus (also ovary, stomach, small bowel, bile ducts, ureter) 80% overall cancer risk (colon + extra-colonic) |
|
|
Gardner's Syndrom and Turcot's Syndrome
|
Gardner’s Syndrome
associated with extra-gastrointestinal tumors: osteomas (bone tumors, mostly of skull and mandible) cutaneous tumors (fibromas, lipomas, epidermal cysts) desmoid tumors (most commonly in the abdomen) Turcot’s Syndrome associated with brain tumors: medulloblastoma glioma |
|
|
FAP Dx and Tx
|
Phenotype identified endoscopically
Treatment: Total proctocolectomy Ileostomy Ileal-Pouch-Anal Anastamosis (IPAA) Timing depends on size and histology of polyps many can wait until completion of high school |
|
|
Peutz Jeghers Syndrome
|
autosomal dominant
characterized by multiple pigmented spots on the lips and buccal mucosa associated with hamartomas small bowel colon stomach typically present in third decade with: intussusception obstruction bleeding 15 fold increased risk of cancer at any site: colon stomach small intestine these three-adenomatous change occurring in hamartomas, leading to the adenoma-carcinoma sequence pancreas breast ovary lung |
|
|
Clinical presentation of CRC
|
40% abdominal pain
40% rectal bleeding or melena 40% change in bowel habit 20% weakness 10% anemia alone 5% weight loss Right colon lesions tend to present with blood loss Left colon lesions tend to present with pain, altered BM Patients presenting with pain have a worse prognosis |
|
|
Test for the Diagnosis of Colon Cancer
|
Colonoscopy - the best test to diagnose CRC
the best sensitivity and specificity allows biopsy of any lesions found detects any synchronous cancers and removal of any synchronous benign polyps Barium Enema – 50% sensitivity CT (routine) - poor sensitivity for intraluminal lesions main utility is to detect metastases (liver, lymph nodes) CT colonography - sensitivity of up to 90% for CRC positive results require colonoscopy for biopsy |
|
|
Clinical Staging of Colon Cancer
|
Physical examination
hepatomegaly, lymphadenopathy, ascites Laboratory: liver function tests, CEA Colonoscopy Evaluate for synchronous lesions Synchronous: additional primary tumor(s) present at initial diagnosis Metachronous: additional primary tumor(s) developing >6 months later Imaging: CT of abdomen and pelvis (+/- chest) imaging is poor for detecting peritoneal metastases MR and PET offer no special advantage EUS for rectal cancer |
|
|
main role of staging
|
prognostic and to guide therapy
endoscopy vs surgery vs surgery and chemo or just chemo |
|
|
Tx of Colon Cancer
|
endoscopic polypectomy
for Tis - T1, well-differentiated cancer in pedunculated polyps surgical resection for cure: 5 cm margins and regional lymphadenectomy required for flat polyps, T2 lesions, or if poorly differentiated for palliation: of obstruction or bleeding chemotherapy for Stage III and IV disease FOLFOX (FOLinic acid, Flourouracil, OXalipitin) Rectal Cancer radiation and chemotherapy (5-FU) for Stage II and III |
|
|
Methods for screening of CRC
|
Fecal occult blood-every yr, not very sensitive
Flexible sigmoidoscopy-5yrs-fallen out of favor. CT colonography-5yrs Colonoscopy-10 yrs |
|
|
preferred methid for screening patients at increased risk for colon cancer
|
colonoscopy
|
|
|
Interval for screening if a first degree relative <60 has CRC
|
every 5 yrs after age 40
|
|
|
Personal Hx of colon adenoma interval for screening
|
3-5 yrs
|
|
|
Personal Hx of Colon Cancer
|
1, 3, then 5
|
|
|
Personal Hx of Ulcerative Colitis
|
every year, starting after 8-10yrs of pancolitis
|
