Colon CA Flashcards
risk factors for colon cancer
diet and geography (less colon CA in Japan, China), age, family hx, chronic colitis, adenomas, previous colorectal CA
What is the adenoma-carcinoma sequence
normal dysplasia –> adenoma (APC mutations) –> severe dysplasia –> cancer. usually takes about 10 yrs for the whole progression to occur.
Other early mutations: KRAS, p53
Polyps are ASYMPTOMATIC: this is why we must screen.
staging for colon cancer
A: in the mucosa B: muscularis C: through the muscularis or has a node D: metastatic A has very good prognosis; D has very poor prognosis
common metastatic sites from colorectal cancer
colon: drains through regional lymph nodes and to liver
rectum: has systemic drainage, so mets can end up in the lung
treatment of liver mets
we can actually try resecting or ablating up to one met in the liver. we can also give chemo, either systemically or infused through the hepatic artery
colonoscopy recommendations for people with normal risk
preferred: colonoscopy every 10 yrs starting at age 50, or age 45 if African American
(or a flex sig q5 at 50, or a virtual colonoscopy, or annual hemeoccult starting at 50)
Which pts are at higher risk for colorectal cancer?
chronic IBD, like UC or crohn’s
personal hx of prior adeoma
family hx or CA syndrome: FAP, HNPCC
Why does dietary fiber reduce colon cancer?
dilutes carcinogens, fermentation to short-chain fatty acids, shortens transit time, binds bile acids, and may contain anticarcinogens
guidelines for screening for colorectal CA in terms of family hx
a 1st degree relative with colon cancer or advanced adenoma > 60 = no incr. risk
a 1st degree relative with RCR or advanced adenoma under 60, or TWO 1st degree relatives at any age: colonoscopy q 5 yrs starting at age 40 or 10 yrs younger than the age of youngest affected family member
FAP: familial adenomatous polyposis: what is it?
HUNDREDS of polys, which may even be in the small intestine or stomach. due to an APC gene mutation (which is a tumor suppressor gene).
FAP: extraintestinal features?
congenital hypertrophy of retinal pigment, abnormal dentition, brain tumors, thyroid tumors, osteomas, epidermal cysts, desmoid tumors (non-malignant but can become scars that will obstruct the kidneys, and can’t be removed)
Guidelines for pts with FAP
annual flex sig starting around puberty. remove whole colon if they have hundreds of polyps
hereditary nonpolyposis colorectal cancer: what is it?
early age at onset, multiple primary cancers, esp. in proximal colon. few or no adenomas. autosomal dominance. also see endometrial CA due to mismatch repair gene mutations
HNPCC criteria
3 or more CRC 2 or more generations one case a 1st degree relative of the other 2 one affected age by 50 FAP excluded
HNPCC extracolonic malignancies
endometrium, stomach, biliary, urinary, ovary small bowel, uroepithelium, sebaceous gland neoplasia
