Question: In asymptomatic patients at normal or above-average risk, how effective are specific screening techniques for colorectal cancer?
Data sources: Studies were identified by searching MEDLINE (1966 to January 2001), reviewing the references of reviews published before January 2001, and surveying content experts.
Study selection: English-language studies were selected if they evaluated Hemoccult testing, flexible sigmoidoscopy, or genetic testing as the first step in a multiphase secondary prevention strategy or colonoscopy as a single-phase secondary prevention strategy in both asymptomatic and high-risk patients. Studies that screened with digital rectal examination and double-contrast barium enema were excluded.
Data extraction: Data were extracted on patient characteristics, duration of follow-up, and main outcome measures.
Main results: For patients at average risk, evidence existed to support the use of annual or biennial fecal occult blood testing (FOBT) (from randomized controlled trials [RCTs]) for asymptomatic patients > 50 years of age. 4 RCTs assessed the value of screening with the Hemoccult test in average-risk patients and found that the risk for death from colorectal cancer was reduced with Hemoccult screening in patients > 50 years of age (relative risk reduction 16%, 95% CI 7 to 23, approximately 1 death from colorectal cancer would be averted for every 1000 screened over a 10-y period). Evidence for the effectiveness of flexible sigmoidoscopy in average-risk patients with an outcome of death was only available from case–control studies. 3 RCTs suggested that flexible sigmoidoscopy might be superior to FOBT in detecting adenomas and possible cancer. However, these trials were small. The evidence for whether 1 or both of FOBT and sigmoidoscopy should be done was unclear, as was the evidence about the use of colonoscopy as an initial screening test. For patients at above-average risk, low-quality evidence (retrospective cohort studies and case series) supported either genetic testing or flexible sigmoidoscopy of patients at risk in familial adenomatous polyposis kindreds and screening with colonoscopy of patients in kindreds with hereditary nonpolyposis colon cancer. The evidence regarding use of colonoscopy for persons who have a family history of colorectal polyps or cancer was unclear.
Conclusion: In patients > 50 years of age at average risk, Hemoccult screening reduces the risk for death from colorectal cancer.