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Fecal DNA Testing for Colorectal Cancer Screening

The high cost and low sensitivity of this test suggest that the time has not come yet to use it as a standard screening method.

A number of genetic mutations are associated with colorectal neoplasia and can be detected by fecal DNA analysis of cells that are exfoliated from colorectal polyps and cancers. In previous small studies of patients with known colorectal cancers, the sensitivity of fecal DNA testing ranged from 61% to 91% (Journal Watch Feb 8 2002 and Journal Watch Nov 21 2000). In this study, researchers assessed the performance of fecal DNA analysis and the Hemoccult II fecal occult blood test in 2507 average-risk, asymptomatic people (mean age, 70) who underwent screening colonoscopy at 81 U.S. locations. The study was sponsored by the developer of the fecal DNA test.

According to colonoscopy results, 31 subjects had cancer, and 403 had advanced adenomas. The sensitivities of fecal DNA and Hemoccult II tests for detecting cancers were 52% and 13%, respectively. For detecting advanced neoplastic lesions (cancers or advanced adenomas), sensitivities of the two tests were 18% and 11%. Specificities of the two tests were 94% and 95% for the 1423 subjects who had negative colonoscopies.

Comment: In this colorectal cancer screening study, fecal DNA testing was more sensitive than Hemoccult II, but less sensitive than has been reported previously in small studies of cancer patients. An editorialist discusses several problems with fecal DNA analysis, including its high cost (US$400-$800) and fairly low positive predictive value, and concludes that it is not yet ready for widespread use as a screening test.

— Allan S. Brett, MD

Published in Journal Watch General Medicine January 4, 2005

Citation(s):

Imperiale TF et al. Fecal DNA versus fecal occult blood for colorectal-cancer screening in an average-risk population. N Engl J Med 2004 Dec 23; 351:2704-14.

• Medline abstract (Free)

Woolf SH. A smarter strategy? -- Reflections on fecal DNA screening for colorectal cancer. N Engl J Med 2004 Dec 23; 351:2755-8.

• Medline abstract (Free)

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