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Cologuard for Colorectal Cancer

Recently, the U.S. Food and Drug Administration approved Cologuard (Exact Sciences) as a screening test for colorectal cancer. Cologuard detectes both hemoglobin and gene mutations associated with colorectal cancer. Patients with positive test results are advised to undergo a diagnostic colonoscopy.

The safety and effectiveness of Cologuard was established in a clinical trial that screened 10, 023 participants for colorectal cancer with Cologuard and a fecal immunochemical test (FIT). Cologuard was more sensitive than FIT. It detected 92 percent of colorectal cancers and 42 percent of advanced adenomas, while FIT detected 74 percent of cancers and 24 percent of advanced adenomas. Cologuard had more false positive results and, therefore, lower specificity than FIT. Cologuard correctly ruled out colon cancer only 87% of the time versus 95% for FIT.

Cologuard’s lower specificity means that an additional 13% of patients will be referred for unnecessary follow-up colonoscopies. However, the less invasive nature of Cologuard may mean that more people might be willing to be screened for colorectal cancer. If everyone was screened with Cologuard, 87% of colonoscopies could be avoided.

Cologuard costs $599 compared to $25 for FIT. Medicare covers the new test once every three years for Medicare beneficiaries who meet all of the following criteria:

  • age 50 to 85 years,
  • asymptomatic and
  • average risk of developing colorectal cancer

Even though Cologuard was not directly tested against colonoscopy, it is being marketed as an alternative. Approval of the Cologuard does not change current practice guidelines for colorectal cancer screening. The United States Preventive Services Task Force (USPSTF) does not recommend stool DNA testing as a method to screen for colorectal cancer. USPSTF recommends adults age 50 to 75, at average risk for colon cancer, be screened using fecal occult blood testing, sigmoidoscopy, or colonoscopy.

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