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New DNA home test finds colorectal issues

Few people that know about the colonoscopy procedure look forward to actually doing it. There is a new home test that can provide a 90% accuracy in detecting colorectal problems. If you fall in the higher risk categories, e.g. 50 years or older, or a family history of colorectal cancers, you still need to consider getting a colonoscopy.

George W. Bush reflects on colonoscopy while president
Photo by Alex Wong/Getty Images

Medline Plus, a publication of the National Institute of Health (NIH), released an article on March 19, 2014 titled New Stool Test Shows Promise as Colon Cancer Screen. The research was published in the March 19, 2014 issue of the New England Journal of Medicine. The research was funded by Exact Sciences Corp., the maker of Cologuard.

Cleveland Clinic provides a description of the complete procedure. A colonoscopy involves an examination by a physician using a camera that is inserted in the colon to check for cancers, tumors or polyps. Other instruments are available to the physician to take tissue samples, excise polyps, and record the location of cancers and tumors during the procedure. Fortunately the standard procedure involves a muscle relaxant and an amnesiac so you don't remember much after getting it done. Take a friend with you to remember what the doctor tells you about your results and any follow-up.

Until recently, colonoscopies were either done every 10 years from the age of 50, or whenever blood was detected in the stool. Fecal immunochemical testing (FIT) shows results if blood is detected. There are many cases where a colon cancer does not have a loss of blood, or blood is a very late indication that a cancer or tumor exists.

The DNA home test kit is not yet FDA approved. The product is called Cologuard. It indicates if specific DNA related to cancers is detected in the stool. The manufacturer claims better than 90% accuracy in detecting colon cancers.

A report on the effectiveness of the DNA based test was released by Dr. Steven Itzkowitz, director of gastroenterology fellowship program at the Icahn School of Medicine at Mount Sinai NYC. Itzkowitz summarized the results as being an improvement over existing home or office screening tests.

“That kind of result is really unprecedented for a noninvasive stool-based screening. By increasing the pick-up rate in this way, we found that the new test had 92 percent sensitivity for detection of colorectal cancer. Commonly used stool tests such as FIT (fecal immunochemical testing) rely on detecting blood in the stool. This new multi-target test checks for blood as well as abnormal DNA coming from the tumor."

The American Cancer Society (ACS) reports on deaths due to all cancers. Colorectal cancer is the third leading cause of cancer-related deaths in the United States when men and women are considered separately, and the second leading cause when both sexes are combined. It is expected to cause about 50,310 deaths during 2014.

Early detection of colorectal diseases is the key to successful treatment. The normal examination procedure for a colonoscopy has a difficult preparation process, is expensive, and serious and sometimes fatal perforations of the bowel can occur. Colonoscopies have particular difficulties in detecting flat lesion cancers in the bowels.

The procedures and conclusions of the research are provided in the NIH article.

“Nearly 10,000 men and women aged 50 and older were screened for colon cancer and precancerous polyps at one of 90 sites across the United States and Canada. All were considered at average risk for colon cancer.

Each patient was screened three ways: a standard colonoscopy; a commercially available fecal test (FIT); and the new DNA test, which requires patients to collect their own stool sample at home and mail it in for laboratory analysis.

Colonoscopy screenings unearthed colon cancer in 65 participants, while another 757 were found to have advanced precancerous lesions. The new test accurately detected 60 of those 65 cancers. The FIT test spotted only 48 cancers, with an accuracy rate of 74 percent compared to 92 percent for the new test.

The DNA test was less accurate with respect to precancerous lesions, spotting about 42 percent of cases. FIT detected roughly 24 percent of precancerous lesions. Cologuard's sensitivity was 69 percent for precancerous polyps most likely to progress to cancer versus 46 percent for the FIT test.

However, the DNA test was more likely to falsely suggest the presence of cancer than either a colonoscopy or FIT testing.”

Itzkowitz acknowledged that the new test is not perfect, but pointed out that there are also issues with a colonoscopy. He says that the Cologuard test should be used to find issues that may require resolution through a follow-up colonoscopy.

Some of the results have been verified by Dr. Frank Sinicrope from the Mayo Clinic in Rochester, MN. Sinicrope is professor of medicine and oncology as was not involved in the initial study. Sinicrope summarized his conclusions about Cologuard testing.

“These data demonstrate the superiority of stool DNA testing compared to FIT for colorectal cancer screening. He also suggested that the Cologuard method might offer some advantages over standard colonoscopies. In particular, he pointed to the DNA test's success in identifying certain advanced-stage polyps, noting such precancerous growths are typically flat and "located in the right side of the colon and are difficult to detect during a colonoscopy."

For those at the age of 50 or beyond that have not had a FIT or colonoscopy, it is generally recommended to at least do the FIT screening. When the Cologuard test becomes available, it should be considered for those at risk. Colorectal cancer often kills by spreading to the bones and other organs in the body. It is critical to detect problems before they become advanced stage cancers. This new test will assist in early detection.

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