© copyright annals of internal medicine, 2014 ann int med. 160 (5): itc5-1. * for best viewing:...

© Copyright Annals of Internal Medicine, 2014Ann Int Med. 160 (5): ITC5-1.

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in the clinic

Screening for Colorectal Cancer


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


Does screening prevent CRC?

Prevents disease-associated morbidity and mortality

Also reduces cancer incidence

Precancerous adenomatous polyps identified and removed


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


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%


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


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


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


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


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


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


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


At what age should patients begin screening?

Average-risk persons:

Initiate screening at age 50


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


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


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

© copyright annals of internal medicine, 2014 ann int med. 160 (5): itc5-1. * for best viewing:...

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