Imagine being able to spot genetic abnormalities linked to colon cancer without an invasive colonoscopy.
That was the goal of a study recently published in The New England Journal of Medicine. Researchers found that the “Cologuard” test, which was developed and patented by Exact Sciences, can pinpoint both occult blood and abnormal DNA shed by polyps and cancerous tumors.
The test is meant to be used by individuals ages 50 and older for screening—all men and women over 50 are considered to be at “average risk” for colon cancer and are candidates for screening. Cologuard is not meant for younger patients, and also not for those who have symptoms or who have a high-risk syndrome.
Unlike the fecal immunochemical test (FIT), the new test can be done from home. The stool sample collected by the patient doesn’t have to be frozen—it is simply shipped to a lab. Polyps and cancers can develop on the inner lining of the colon, so abnormal cells shed abnormal DNA into the stool before they release them into the blood.
How Does It Work?
The researchers compared the FIT test to the Cologuard test. They studied 10,000 people at average risk who were older than 50 who submitted samples for both tests. All of the subjects then had colonoscopies.
The Cologuard test detected 92 percent of colorectal cancers in patients versus 74 percent for the FIT. It also spotted 42 percent of advanced pre-cancerous lesions, compared to 24 percent for FIT.
Dr. Steven Itzkowitz, study author and professor of medicine at the Icahn School of Medicine at Mount Sinai Hospital, who is also the director of the gastroenterology fellowship program, noted that the FIT only detects occult blood in stool—some cancers and most polyps do not bleed substantially.
“Since cancers and polyps shed abnormal DNA into the stool, this enhances the ability to detect these lesions,” he said, adding that the Cologuard isn’t a genetic test in a traditional sense.
The researchers said that the test may be used as an initial screening tool, but could also be useful for high-risk patients to use between colonoscopies to make sure that lesions are not developing before their next colonoscopy exam.
What’s Next for Cologuard?
Itzkowitz said that it would help to have the test endorsed by medical societies that create screening guidelines. The next step is to have the test approved by the U.S. Food and Drug Administration (FDA). He added that future research could address how often the test should be performed.
Could the Cologuard eventually replace routine colonoscopies?
“Colonoscopy is such an important tool in medicine for preventing and treating colon cancers and polyps, and studies indicate that when colonoscopy is used for screening, it is highly effective for reducing colon cancer incidence and even deaths,” Itzkowitz said. “We do not anticipate that any non-invasive test will replace colonoscopy, but rather, that it will be another available screening option.”
Assuming the test is approved by FDA, Itzkowitz said he anticipates that the Cologuard test would be the first-line screening tool for many patients. After a positive test result, the patient would undergo a colonoscopy to confirm whether or not they have a tumor or precancerous polyp.
Treatment would not begin until a cancer diagnosis, which would ultimately be confirmed via a colonoscopy.