The U.S. Food and Drug Administration this week approved Cologuard, the first stool-based colorectal screening test that detects the presence of blood and DNA mutations that may indicate the presence of abnormal growths, especially colon cancer.

Colorectal cancer primarily affects people age 50 and older, and is the third most common cancer and the second leading cause of cancer-related death in the United States. Screening is effective at reducing  illness and death, but only two-thirds of adults in this age group are getting the invasive colonoscopy tests. The CDC estimates that if everyone over 50 received the recommended screening tests, at least 60 percent of colorectal cancer deaths could be avoided. Now, people may have an easier option for screening.

The safety and effectiveness of Cologuard was established in a clinical trial that screened 10,023 subjects. The trial compared the performance of Cologuard to the fecal immunochemical test (FIT), a commonly used non-invasive screening test that detects blood in the stool. Cologuard accurately detected cancers and advanced adenomas more often than the FIT test. Cologuard detected 92 percent of colorectal cancers and 42 percent of advanced adenomas in the study population, while the FIT screening test detected 74 percent of cancers and 24 percent of advanced adenomas.

The test is still not perfect. Cologuard tallied many false positives. 13 percent of the positive test results were actually clear of cancer, compared to FIT which was inaccurate in only 5 percent of its positive results.

Colorectal cancer occurs in the colon (large intestine) or rectum (the passageway that connects the colon to the anus). Most colorectal cancers start as abnormal raised or flat tissue growths on the wall of the large intestine or rectum (polyps). Some very large polyps are called advanced adenomas and are more likely than smaller polyps to progress to cancer.

Using a stool sample, Cologuard detects hemoglobin, a protein molecule that is a component of blood. Cologuard also detects certain mutations associated with colorectal cancer in the DNA of cells shed by advanced adenomas as stool moves through the large intestine and rectum. Patients with positive test results are advised to undergo a diagnostic colonoscopy.

“This approval offers patients and physicians another option to screen for colorectal cancer,” said Alberto Gutierrez, Ph.D., director of the Office of In Vitro Diagnostics and Radiological Health at the FDA’s Center for Devices and Radiological Health. “Fecal blood testing is a well-established screening tool and the clinical data showed that the test detected more cancers than a commonly used fecal occult test.”

Today’s approval of the Cologuard does not change current practice guidelines for colorectal cancer screening. Stool DNA testing (also called “fecal DNA testing”) is not currently recommended as a method to screen for colorectal cancer by the United States Preventive Services Task Force. Among other guidelines, the USPSTF recommends adults age 50 to 75, at average risk for colon cancer, be screened using fecal occult blood testing, sigmoidoscopy, or colonoscopy.

The Centers for Medicare & Medicaid Services already proposed national coverage for Cologuard to “provide the innovative screening test to help in the early detection of colorectal cancer in seniors.”

Cologuard, manufactured by Exact Sciences in Madison, Wisconsin, will cost $599 per patient.That compares to about $25 for a traditional stool blood test, according to CBS News.

(WATCH a video below or READ more from CBS News)

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