75 %
Average risk (sporadic)
15–20 %
Family history of colorectal cancer
3–8 %
Hereditary nonpolyposis colorectal cancer
1 %
Familial adenomatous polyposis
1 %
Ulcerative colitis
Average-risk persons have no symptoms associated with colorectal cancer, no personal history of colorectal cancer or adenomatous polyps, no family history of colorectal neoplasia, no inflammatory bowel disease, and no unexplained anemia.
In October 2008, the US Preventive Task Force recommended that average-risk persons should undergo one of the following screening regimens, beginning at age 50 and continuing until age 75 (Table 39.2):
Table 39.2
Screening for colorectal cancer and polyps
Risk category | Screening method | Age to begin screening |
|---|---|---|
Average risk | Choose one of the following: | 50 years |
1. High-sensitivity FOBT annuallya | ||
2. Flexible sigmoidoscopy every 5 years combined with high-sensitivity FOBT every 3 yearsa | ||
3. Colonoscopy every 10 years | ||
Family history | Choose one of the following: | 40 or 10 years prior to diagnosis of the youngest affected family member, whichever is earliest |
1. Colonoscopy every 10 years | ||
2. Colonoscopy every 5 years if diagnosis of colorectal cancer was made before age 60 | ||
3. Air-contrast barium enema every 5 yearsb | ||
Lynch syndrome | Colonoscopy every 1–3 years | 21 years |
Genetic counseling | ||
Consider genetic testing | ||
Familial adenomatous polyposis | Flexible sigmoidoscopy or colonoscopy every 1–2 years | Puberty |
Genetic counseling | ||
Consider genetic testing | ||
Inflammatory bowel disease (ulcerative colitis and Crohn’s colitis) | Colonoscopy with random biopsies for dysplasia every 1–2 years | 7–8 years after the onset of pancolitis; 12–15 years after the onset of left-sided colitis |
High-sensitivity fecal occult blood testing (FOBT) annually
Flexible sigmoidoscopy every 5 years with high-sensitivity FOBT every 3 years
Colonoscopy every 10 years
The American College of Gastroenterology guidelines (updated in 2008) outline a “preferred” strategy for colorectal cancer screening suggests that patient compliance increased when there is a “preferred” strategy rather than a “menu” of options. Preferred screening recommendations for average-risk persons beginning at age 50 included one of the following (screening should begin at age 45 in black patients):
Colonoscopy every 10 years
Annual fecal immunochemical test (FIT) for blood
Alternative prevention tests
Flexible sigmoidoscopy every 5–10 years
CT colonography every 5 years
Alterative cancer detection tests
Annual Hemoccult SENSA
Fecal DNA testing every 3 years
Fecal Screening Tests
Several large randomized controlled trials as well as high-quality systematic reviews have shown that annual or biannual testing for fecal occult blood, with complete diagnostic evaluation of the colon (primarily with colonoscopy) for patients with a positive FOBT, reduces mortality from colorectal cancer.
Testing of three samples is more sensitive than testing of a single sample.
An alternative method of FOBT is the fecal immunochemical test which employs antibodies specific to blood components.
A major drawback to using stool testing as a screening technique is poor compliance. Only 38–60 % of the patients in prospective trials completed all the planned FOBT tests, and use of FOBT in the general population is estimated to be lower than that in the research environment.
The steps necessary for adequate sample collection, combined with dietary restrictions to avoid agents that can cause false-positive and false-negative results may also hinder compliance with FOBT.
Proper performance of FOBT involves the sampling of atraumatically obtained stool from three consecutive bowel movements in a patient who has not ingested red meat, aspirin, nonsteroidal inflammatory medications, turnips, melons, salmon, sardines, horseradish, or vitamin C for the 2 days preceding the test and throughout the test period.
FOBT should not be confused with random stool guaiac testing, which is the analysis of stool found on digital rectal exam for blood. The lack of adequate diet and medication restriction prior to the test, potential for trauma to the anal canal during digital rectal examination, and the inability to reliably obtain stool from the distal rectum make the test unreliable.
In the future, immunochemical techniques or genetic analysis of cellular material in stool may prove to be more effective than current FOBT technology.
In 2004, the Colorectal Cancer Study Group compared Hemoccult II with fecal DNA testing (21 mutations) in 5,486 patients who subsequently underwent a colonoscopy. The sensitivity of the fecal DNA test for advanced neoplasms (cancer, adenomas with villous or dysplastic histology, adenomas ≥10 mm) was 18 % in comparison to Hemoccult II, which was 11 %. The specificities were 94 and 95 %, respectively. Other studies have been less convincing and it remains unclear whether there are adequate data to support widespread use of fecal DNA tests as a viable colorectal cancer screening strategy.
Sigmoidoscopy
The effectiveness of sigmoidoscopy as a screening tool depends on its ability to detect cancers and adenomatous polyps in the distal colon. If adenomatous polyps are found at flexible sigmoidoscopy, colonoscopy should be strongly considered because almost one-third of such patients will have neoplastic lesions in the proximal colon.
The Prostate, Lung, Colon, and Ovary Trial supported by the National Cancer Institute evaluated flexible sigmoidoscopy in a randomized, controlled setting and found that incidence was decreased by 21 % and death was decreased by 26 % over an average of almost 12 years.
In this trial, wide variability in polyp detection rate was observed between endoscopists, which raises concern regarding adequacy of the examination in the hands of inexperienced endoscopists.Related posts:
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