© copyright annals of internal medicine, 2014 ann int med. 160 (5): itc5-1. * for best viewing:...
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© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
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© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
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© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
in the clinic
Screening for Colorectal Cancer
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
Can patients reduce their risk forCRC by modifying their healthbehaviors or using certain drugs? Health behaviors that may reduce risk
Moderate intake red meat and saturated & unsaturated fat
Regular physical activity
Maintenance of normal body weight
Avoidance of alcohol and tobacco
Consumption of 5–7 daily servings fresh fruits, vegetables
Diet rich in calcium, folate, selenium, vitamins A, D, E
Postmenopausal estrogen, aspirin and other NSAIDs
Balance of benefits vs. harms doesn’t favor use of estrogen or NSAIDS for primary prevention
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
Does screening prevent CRC?
Prevents disease-associated morbidity and mortality
Also reduces cancer incidence
Precancerous adenomatous polyps identified and removed
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
CLINICAL BOTTOM LINE: Prevention… Health behaviors can decrease CRC risk
Improving dietary intake
Increasing physical exercise
Taking aspirin regularly
Screening plays a major role in primary prevention
Powerful way to reduce CRC incidence and mortality
Proven public health benefit
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
What are the precursors of CRC?
Adenomatous polyps
Focal point of screening: identifying and removing polyps
Terminology for adenomas: tubular, tubulovillous, villous, mixed, serrated
Advanced adenomas Measure ≥1 cm
Foci of high-grade dysplasia
Tubulovillous or villous component
Increased long-term risk for cancer
Merit more frequent surveillance
Prevalence at screening colonoscopy: 5%–10%
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
Serrated lesions
Originally not believed to be associated with cancer
Subset now known to be colon cancer precursors: “Sessile serrated adenoma” and “sessile serrated polyp”
Number + type of adenoma dictate surveillance interval
Occurrence of CRC after screening = interval cancer
Due, in part, to missed lesions (suboptimal colonoscopy)
Accounts for 5%–8% of all cases
Adenoma detection rate (ADR): % cases in which adenomas detected
Guidelines recommend overall ADR ≈25% for endoscopist
Lower ADRs: increased risk for (preventable) CRC
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
Fecal occult blood testing (FOBT)
Positive results require follow-up colonoscopy
Many false-positives; repeated testing needed
What methods are effective in CRC screening?
Fecal immunochemical testing (FIT)
Measures intact human globin protein (vs. heme)
Requires 1 stool specimen vs. 3 for FOBT; less stool handling, more specific for lower GI bleeding
Detects more advanced adenomas than FOBT
Lower cutoff for positive results increases sensitivity for neoplasia detection
Flexible sigmoidoscopy Greater benefit in the distal vs proximal colon
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
Colonoscopy
Visual exam of entire colon, combines Dx and treatment
Increased detection of adenomas and carcinomas compared with FOBT, FIT, or flexible sigmoidoscopy
Disadvantages: colonic prep, sedation, lost work time and need for transport, cost, invasive nature; complication risk
CT Colonography
Noninvasive and can examine entire colon
Minimal complication rate
Effective visualizing lesions that protrude into lumen
Colonic preparation required
Colonoscopy required to remove detected polyps
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
What are the emerging CRC screening techniques?
Fecal DNA testing
Colonic mucosal cells continually shed into fecal stream
So are cells shed by colonic neoplasms
Test allows identification of cells with specific genetic or epigenetic changes
Noninvasive detection of CRC, perhaps large adenomas
May detect serrated polyps
Fecal DNA + FIT: 92% sensitivity, 87% specificity for CRC
Cost: primary obstacle that inhibits broader adoption
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
How should clinicians and patients select from among different screening methods?
No clear evidence that one outperforms another
Each test has advantages and disadvantages
Colonoscopy favored in U.S., but not necessarily best test
Compliance better with simpler, less demanding fecal test?
When choosing screening option, weigh:
Costs
Availability
Convenience
Patient preference
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
Is CRC screening cost-effective?
CRC screening is considered cost effective
Reduces cancer incidence
Leads to fewer patients requiring treatment
Cost for treating established CRC has accelerated
Newer targeted therapies are expensive
Ensuring the cost-effectiveness of screening
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
What are the risks for patients?
Most adenomas detected and removed via screening are unlikely to progress to CRC
The screening process operates on “overkill”
We can’t tell which adenomas will progress, so all removed
Approach substantially reduces CRC mortality + incidence
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
At what age should patients begin screening?
Average-risk persons:
Initiate screening at age 50
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
How frequently should patients repeat screening? If no adenomas are found…
FOBT or FIT: repeat annually
Flexible sigmoidoscopy: repeat every 5 years
Colonoscopy: repeat every 10 years
If adenomas detected: next recommended interval test…
Hyperplastic polyp: 10 years
1-2 Nonadvanced adenomas: 5–10 years
≥3 Nonadvanced adenomas: 3 years
Advanced adenoma (≥1cm, with villous components, or with high-grade dysplasia): 3 years
Type, number, size of polyps guides follow-up frequency
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
At what age should average-risk patients stop screening?
Depends on life expectancy and anticipated benefit
Limited life expectancy reduces potential benefit
Harms of screening may increase for elderly patients
OK to stop at age 75 years or if life expectancy <10 yrs
© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.
CLINICAL BOTTOM LINE: Screening…
For general population: Screening is a key component of preventive health
Cost-effective
Should begin at 50 years of age
Continue at regular intervals well into later adulthood
Unless there is a compelling contraindication
Accomplished through a number of accepted methods
Fecal testing, flexible sigmoidoscopy, colonoscopy
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