A new test that screens for colon cancer and can be done at home is now available. Developed by Mayo Clinic gastroenterologist David Ahlquist, MD, and Exact Science, the test, known as Cologuard, detects cancer-related DNA in the stool and received FDA approval in August.
According to the Centers for Disease Control and Prevention, 135,260 Americans were diagnosed with colorectal cancer in 2011. Associated Press (AP) reports that 52,000 deaths from the disease are expected this year alone.
Colonoscopy — the insertion of a thin tube with a tiny camera into the large intestine while under a general anesthesia, — is the “gold standard” for colon cancer screening for anyone 50 years and older. However, many experts say that the best screening test is the one people are willing to get, and only about 60 percent of those for whom the test is recommended actually have the procedure.
Noninvasive Cologuard tests for blood in the stool that may indicate a tumor, but it also looks at the DNA from abnormal cells that are naturally shed into the colon and that could be signs of cancerous or precancerous polyps. A stool sample is collected and sent to a laboratory and if it comes back positive, a colonoscopy is recommended.
Cologuard was not tested against colonoscopy for screening, but it is being presented as an alternative to the test. In clinical trials that compared the product to an older stool-blood test, Cologuard detected 92 percent of colorectal cancers and 42 percent of advanced precancerous growths. The older stool-blood tests found 74 percent of cancers and 24 percent of growths. The downside is that Cologuard had a 13 percent false positive rate compared with the older stool test’s 5 percent.
Cologuard costs $599 versus about $25 for the older stool-blood tests. It is covered by Medicare but not by private insurers.
The hope is that because this is a simpler, less expensive colon cancer screening alternative, it will be used by people who are reluctant to undergo a colonoscopy. Still, some experts are only cautiously optimistic.
“You’d rather have more options than not, but I don’t think there is enough data to declare this test superior to any other test” because of the false positives and lack of proof that it will save lives, Kenneth W. Lin, MD, associate professor, Georgetown University and former staff doctor for the preventive services task force, told AP. But he added, “It definitely has some promise.”