A non-invasive test that analyzes mutated DNA in feces may be a useful method of detecting colorectal cancer in average risk, asymptomatic individuals, according to a study in the December 23rd issue of The New England Journal of Medicine.
In the study, 4404 average-risk adults age 50 or older underwent fecal occult-blood testing with the Hemoccult II, fecal DNA testing, as well as colonoscopy — the reference standard.Dr. Thomas F. Imperiale from the Indiana University School of Medicine and the Regenstrief Institute in Indianapolis and multicenter colleagues compared test results in a random subgroup of 2507 subjects seen in private-practice or university-based settings.The fecal DNA test detected just over half (16 of 31) of all invasive colorectal cancers (TNM stage I, II, or III), for a sensitivity of 51.6%, they report.”The fecal DNA test was better than the Hemoccult II, the current standard noninvasive screening test,” Dr. Imperiale told Reuters Health, noting that the Hemoccult II detected only 4 of 31 invasive colorectal cancers in the same population, for a sensitivity of 12.9%.Moreover, the sensitivity of the fecal DNA test was “more than twice” that of Hemoccult II for detecting adenomas containing high-grade dysplasia (32.5% vs 15.0%). Among 418 individuals with advanced neoplasia, the DNA fecal test had a sensitivity of 18.2% compared with a sensitivity of 10.8% for Hemoccult II.”Specificity in subjects with negative findings on colonoscopy was 94.4% for the fecal DNA panel and 95.2% for Hemoccult II,” the authors also report.Dr. Imperiale and colleagues point out that while “the majority of neoplastic lesions identified by colonoscopy were not detected by either noninvasive test, the multitarget analysis of fecal DNA detected a greater proportion of important colorectal neoplasia than did the Hemoccult II without compromising specificity.”They emphasize, however, that the place of DNA fecal testing in colorectal cancer screening remains to be determined.Dr. Steven H. Woolf, from the Virginia Commonwealth University in Richmond, agrees, noting in an editorial that while testing stool for DNA is a “potentially smarter strategy” than testing it for occult blood, numerous questions remain including issues of generalizability, superiority, testing intervals, not to mention affordability.The price tag for fecal DNA testing is $400 to $800 compared with a cost of $3.00 to $40 for fecal occult blood testing, he notes.The current study was funded by grants from EXACT Sciences, Inc., manufacturer of the stool DNA panel.(Source: N Engl J Med 2004;351:2704-2714,2755-2758: Reuters Health: Megan Rauscher: Oncolink: December 2004.)