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Recommended Screening Methods for Persons at Average Risk of Developing Colorectal Cancer

for Health Care Providers

Table 1. Recommended Screening Methods for Persons at Average Risk of Developing Colorectal Cancer

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Screening Method Recommended by USPSTFAccuracy and EffectivenessComments/ Limitations/Risks
Colonoscopy every 10 years↓mortality >50%

Sensitivity:

  • 90% for polyps >1cm
  • 75% for polyps =1 cm
Colonoscopy has been the reference standard against which FOBT and sigmoidoscopy have been studied
Complete bowel prep required.

Colonoscopy can visualize entire colon. Suspicious lesions can be removed for biopsy and as treatment.

Greater yield of colonoscopy (most sensitive test for polyps) must be weighed against risks of perforation, bleeding, and conscious sedation, as well as inconvenience of full colonic preparation and conscious sedation.

Risk of screening colonoscopy
  • Any major complication: 0.3%
  • Perforation: 0.05%
  • Bleeding: 0.15-0.18%
Risk of colonoscopy as therapeutic procedure is higher
  • Perforation: 0.07-0.72%
  • Bleeding: 0.2-2.7%
Risks of procedure are greater in persons >70 years of age, but so are benefits, as proximal lesions are more common in this population.
Home FOBT every year↓ mortality 15-33%, depending on frequency of screening

Positive predictive value (percentage of patients with positive test result who have cancer or large polyp):

  • Rehydrated specimens: 6-8%
  • Unrehydrated specimens: 20-40%
Rehydration before adding developer:

  • ↑ sensitivity from 40% to >50%
  • ↓ specificity from 98% to 90%
  • Leads to more colonoscopies
Annual screening found 49% of cancers; 38% of patients tested required colonoscopy

Screening every 2 years found 39% of cancers; 28% of patients tested required colonoscopy
Patient submits three 2-window cards, 1 card each from 3 consecutive stools collected at home.

Do not use DRE to collect specimens.

The American Gastrointestinal Association (AGA) recommends against rehydrating specimens.

If result is positive in any card window, obtain colonoscopy.

FOBT itself is extremely low risk, but leads to many colonoscopies being performed, with associated risks of bleeding and perforation.
Flexible sigmoidoscopy every 5 years↓ mortality 59% for cancers within reach of sigmoidoscope

Sensitivity: 70-80%

Specificity difficult to define
Complete or partial bowel prep required.

Misses lesions proximal to the splenic flexure.

Proximal lesions more common in women than men.

Estimated to find 80% of patients with abnormal findings, as distal abnormalities will prompt examination of entire colon with colonoscopy.

In one study, sigmoidoscopy alone would have missed 65% of women with advanced lesions detected by colonoscopy.

In another study, 52% of patients with advanced proximal lesions (by colonoscopy) had no distal lesions.

Presence of an adenoma generally necessitates full colonoscopy. Controversy exists regarding presence of small tubular adenomas, though many providers would perform colonoscopy.

Complication rate:

  • Perforation: <0.01%
  • Bleeding: 2.5-5.5%
FOBT + flexible sigmoidoscopy every 5 years In one study, rigid sigmoidoscopy + 3-card FOBT (hydrated) detected 76% of advanced lesions vs 70% for sigmoidoscopy alone; 24% of advanced lesions were missed; incidence of death from cancer decreased by approximately 50% in sigmoidoscopy + FOBT group vs sigmoidoscopy alone

Studies of adding flexible sigmoidoscopy to FOBT show doubling of diagnostic yield
Positive FOBT result necessitates full colonoscopy, so perform FOBT before sigmoidoscopy.

Complete or partial bowel prep required before flexible sigmoidoscopy.

From Cancer Screening
Primary Care of Veterans with HIV
Office of Clinical Public Health Programs
Veterans Health Administration, 2009