Colorectal cancer (CRC) remains the second-leading cause of cancer deaths in the United States, and a new multi-marker test for stool DNA (sDNA) developed by Mayo Clinic in collaboration with Exact Sciences Corp. of Madison, Wis., has seen improvements to the effectiveness of screening for CRC and reducing risk. No special preparations are needed for the test, it can be performed on mailed-in samples. This eliminaties the need for an office visit, and it has provides highly accurate at detecting premalignant polyps and early-stage colorectal cancer.
"We have a mandate to improve effectiveness of screening by better use of existing tools and by creating better tools," says David A. Ahlquist, M.D., of Mayo Clinic. "If one had to start all over, the ideal screening test would be noninvasive and affordable; require no bowel prep, medication restriction or diet change; and would detect neoplasms on both sides of the colorectum with high accuracy."
The sDNA test is an automated assay for tumor-specific DNA changes, including methylated BMP3 and NDRG4, a mutant form of KRAS, the β-actin gene, and hemoglobin. In three blinded case-control studies, each involving more than 1,000 patients, that have been published or presented in the past year, detection rates for the critical screening targets have been remarkably high. Detection rates increase with size and progression risk of polyps. Sensitivity was 64 percent for both adenomatous and serrated polyps greater than 1 cm, 77 percent for those greater than 2 cm, and 92 percent for polyps larger than 4 cm. Of critical importance, detection is not affected by location or stage.
Unlike colonoscopy and fecal blood testing, the sDNA test is not operator dependent; it is a standardized automated procedure with results interpreted by a computer. The test is also performed less frequently than fecal blood testing — the most commonly used noninvasive option — thereby providing more opportunities for increasing compliance and reducing costs.
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