Feb27 M1-Colorectal Cancer Screening Flashcards
dx test vs screen
screen = just to check
dx test = suspect disease
signs and symptoms in colorectal cancer
- bowel habit changes
- bleeding (BRBPR)
- abd pain, bloating
- incomplete evacuation
- weight loss (cancer cachexia)
- fatigue (anemia, liver metastases)
(IMPORTANT) big 3 cancers in adults
lung, breast, colorectal
(IMPORTANT) how cancer incidence differs in age groups
adults 30+: the big 3
youth: different cancers have the higher incidences (CNS AND LEUKEMIA in youth)
how incidence and prevalence of CRC (colorectal cancer) changing
worlwide: increasing incidence
Canada: decreasing incidence
Increasing prevalence
normal seq of CRC dev
normal - proliferative epithelium - adenoma - carcinoma
how CRC develops
series of genetic alterations over 7-10 yrs: FIRST HEAT IS APC (adenomatous polyposis coli gene)
order of genetic hits in CRC
APC (get proliferative epithelium), 18q deletion, TP53 = CA
2 hereditary CRC
FAP (familial. no APC). Lynch syndrome (germline mutation in mismatch repair genes)
2 pathways to CRC
- chromosomal instability (sporadic)
- microsatellite unstability (mismatch repair genes)
MMR genes problems (micro sat unstability): CRC is where + often related to what
- right side CRC
- linked with hereditary non polyposis colon cancer (HNPCC)
non modif risk factors in CRC
age, ethnic background (ashkenazi jews and african americans), genetics (heredity)
modif risk factors in CRC
- diet
- phys activity
- meds
- other conditions (diabetes, obesity)
what age CRC risk rises a lot and consequence
50 yrs old. so gvt screening starts at 50
diet factors in CRC
- red meat (iron, N-nitroso compounds, polycyclic aromatic hydrocarbons, heterocyclic amines, heme)
- fruits may help (antioxidants: indoles, carotene)
- dietary fiber: less ADENOMA (should help for less CA in theory)
micronutrients in CRC
Ca, vit D and dairy helps
diet types in CRC
- alcohol bad
- medit diet good
- prudent diet good (poultry, fish, fruits)
meds in CRC
aspirin and NSAIDS reduce CRC risk
obesity, exercise in CRC
- obesity = higher risk
- exercise = less risk
- estrogens (women) decrease risk
fecal occult blood test (FOBT) at home (3x over 7 days): benefit
15-33% reduction in CRC mortality
overt vs obscure vs occult bleeding
overt = see blood obscure = see blod but don't know where it's from occult = only seen on test (not with eyes)
importnt thing in FOBT
helps even more to reduce mortality if done every year instead of every 2 years (age 50 to 74)
(IMPORTANT) DX TEST done if FOBT is positive
FULL OPTICAL COLONOSCOPY
how FOBT helps
indirectly leads us to go and find the polyp and remove it
better version of FOBT
fetal IHC test (FIT test): more SENSITIVE. no diet restriction.
DISTAL GI blood
(IMPORTANT) DX test if FIT test is positive
FULL OPTICAL COLONOSCOPY
NNT of FIT test
- is a good number
to remember in FIT test and FOBT
bleeding may have other cause than CRC (polyp)
radiological tests for CRC screening + in who
- barium enema (double contrast): look for apple core lesion
- virtual colonography: CT scan reconstruct inside of colon
FOR NORMAL ASYMPTOMATIC person
(IMPORTANT) DX test if radiological screening for CRC is positive
FULL OPTICAL COLONOSCOPY
barium enema problems
not best test for sensitivity + not proven to help for CRC mortality
virtual colonoscopy problem
need bowel prep + insufflate air with no sedation, very uncomfortable for pt
optical tests for CRC + important principle
-flexible sigmoidoscopy
-colonoscopy
REDUCE MORTALITY 50%
(EXAM) 6 screening recommendations)
- high sens FOBT or FIT ANNUALLY
- flexible sigmoidoscopy every 5 years + FOBT or FIT annually
- double contrast barium enema every 5 years
- CT colonography every 5 years (air thing)
- colonoscopy every 10 yrs
- fecal DNA testing
(EXAM) preferred strategy for screening
colonoscopy every 10 years
(EXAM) screening for CRC in Quebec
annual FIT
(EXAM) BLOOD in stool or Lynch patients: screening recommendations
annual colonoscopy
(EXAM) why annual FIT test if choose flexible sigmoidoscopy every 5 years
to not miss right sided cancers and polyps. (sigmoidoscopy covers left side, sigmoid and rectum)
(EXAM) where most CRC cancers occur
left side, sigmoid colon and rectum
(EXAM) normal mucosa to cancer time
7-10 years