Stool DNA test good option for cancer screening in remote areas

Volume 5, Issue 1, 2016


The colorectal cancer test may offer more effective prevention and control for Alaska Native people.

Photograph of David A. Ahlquist, M.D.

David A. Ahlquist, M.D.

Cologuard, a noninvasive stool DNA test for colorectal cancer, appears to be a good screening option for Alaska Natives, a population with one of the world's highest rates of colorectal cancer, according to research from the Mayo Clinic Cancer Center and the Alaska Native Tribal Health Consortium published in the journal Mayo Clinic Proceedings in October 2015.

"The remote residence of many Alaska Native people in sparsely distributed communities across vast regions creates a barrier to screening with conventional tools, such as colonoscopy," said David A. Ahlquist, M.D., study author, co-inventor of the stool DNA test, and a Mayo Clinic Cancer Center consultant in gastroenterology and hepatology. "Stool DNA testing, which was recently approved by the Food and Drug Administration, may offer a practical and effective screening method for this population."

The stool DNA test is a noninvasive screening tool that identifies characteristic chemical changes in stool that signal the presence of cancer or precancerous polyps. The test, which requires no bowel preparation and no diet or medication restrictions, can be done from home via a mailed sampling kit.

"Stool DNA detects colorectal cancer and highest-risk precancerous polyps with high accuracy, and its application within a screening program could translate into more effective prevention and control of the leading cancer among Alaska Native people," Dr. Ahlquist said.

In the study conducted from Anchorage, Alaska, 661 Alaska Native participants submitted stool samples prior to a prescheduled screening colonoscopy, which served as the reference standard. Stool DNA testing was performed in separate laboratories by technicians unaware of the clinical source of specimens.

The stool DNA test detected significantly more screen-relevant neoplasms than did the fecal immunochemical test.

The stool DNA test also detected 100 percent (10 out of 10) of colorectal cancers. Stool DNA test sensitivity for precancerous polyps increased significantly in proportion to polyp size and the related risk of progression to cancer. Detection was 80 percent for the largest polyp group (those 3 centimeters or larger).

For the important subset of patients with a sessile serrated polyp type, which accounts for approximately one-third of all colorectal cancers and is typically located on the far side of the colon, differences between stool detection rates were striking. Stool DNA testing detected 67 percent of these polyps larger than 1 centimeter, compared with just 11 percent by fecal occult blood testing.

"The high detection rates of cancer and large polyps by stool DNA that we found in the Alaska Native population are remarkably similar to those demonstrated in the multicenter 10,000 patient screening study of the general U.S. population reported in the New England Journal of Medicine," Dr. Ahlquist said.