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Selective Screening with Colonoscopy?

These authors suggest that sigmoidoscopy might prove sufficient for low-risk patients, but getting any colon cancer screening done remains a challenge.

Compared with sigmoidoscopy, screening colonoscopy allows clinicians to examine more of the colon and, therefore, to miss fewer colonic neoplasms; however, colonoscopy is more invasive and more costly than sigmoidoscopy. These researchers sought to identify people who were at low enough risk for proximal neoplasia that screening sigmoidoscopy would suffice.

Among 3025 people (age, 50 or older) who were screened by colonoscopy, 3% had advanced proximal (to the descending colon) neoplasia (tubular adenoma 1 cm, any villous polyp, high-grade dysplasia, or cancer). Using factors associated with risk for proximal findings (age, sex, and most advanced distal findings), the researchers created a risk index. In a derivation subgroup of 1994 patients, 37% had a low risk score; 0.7% of those with low risk scores had advanced proximal neoplasia. To validate the findings, the researchers tested the scoring system in the remaining 1031 patients: 47% had low scores, and 0.4% of them had advanced proximal neoplasia. In patients with low risk scores, 174 colonoscopies would need to be done to detect one case of advanced proximal neoplasia.

Comment: The authors suggest that, in the future, colonoscopic screening might be limited to those at higher risk for lesions missed by sigmoidoscopy, though they caution that their results need to be validated first. I question whether they have identified a subgroup with low enough risk (about 1%, compared to 3% for the entire cohort). An editorialist points out that successful implementation of the authors' strategy would require that screening sigmoidoscopy be in widespread use (which it is not) and that patients be satisfied with a limited exam (which is unlikely for people choosing an endoscopic screening strategy). He concludes that the real issue remains how to achieve any screening for colon cancer.

— Richard Saitz, MD, MPH, FACP, FASAM

Published in Journal Watch General Medicine January 23, 2004

Citation(s):

Imperiale TF et al. Using risk for advanced proximal colonic neoplasia to tailor endoscopic screening for colorectal cancer. Ann Intern Med 2003 Dec 16; 139:959-65.

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• Medline abstract (Free)

Winawer SJ. Screening sigmoidoscopy: Can the road to colonoscopy be less traveled? Ann Intern Med 2003 Dec 16; 139:1034-5.

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• Medline abstract (Free)