Screening Stool DNA Test Detects Colorectal Cancer

The accuracy of a multi-target stool DNA test (MT-sDNA) compared with fecal immunochemical testing for hemoglobin (FIT) for detection of screening-relevant colorectal neoplasia (SRN) in Alaska Native people has been assessed.

The Alaska Native (AN) people have among the world's highest rates of colorectal cancer—more than twice the rate of Caucasians living in the USA. Colorectal cancer is also the most commonly diagnosed cancer among this population and conventional invasive screening approaches, such as colonoscopy, present access challenges for people in remote Alaskan villages.

Scientists at the Alaska Native Epidemiology Center (Anchorage, AK, USA) working with their colleagues carried out prospective cross-sectional study, to compare the accuracy of MT-sDNA and FIT for detection of screening-relevant colorectal neoplasia in AN people using colonoscopy as the reference standard. The target population comprised asymptomatic persons with any degree of self-reported AN heritage who were 40 through 85 years old, were scheduled for average-risk screening or surveillance colonoscopy. All participants were enrolled from February 6, 2012, through August 7, 2014, provided stool samples for MT-sDNA and FIT testing before prescheduled screening or surveillance colonoscopy.

All specimens were received at a central laboratory within the Mayo Clinic (Rochester, MN, USA) for initial processing and storage. Stool tests were performed in separate clinical laboratories. Stool aliquots were subsequently sent in batches to Exact Sciences Corporation (Madison, WI, USA) for performance of their commercial Cologuard MT-sDNA. On receipt of collection tubes, the commercial OC-Sensor Diana FIT (PolyMedco, Inc.; Cortlandt Manor, NY, USA) was performed.

The scientists found that of 661 average risk Alaska Native people, Cologuard detected 100% (10/10) of colorectal cancers and 52% (24/46) of significant premalignant lesions, adenomas greater than 1 cm in people between the ages of 40 to 85. The detection rate of Cologuard increased to 80% for the largest pre-cancerous lesions greater than 3 cm, which are most likely to progress to cancer. The FIT detected 80% (8/10) of colorectal cancers and only 30% of significant premalignant lesions adenomas that were greater than 1 cm. Cologuard achieved a specificity of 93% and FIT achieved a specificity of 96%.

David Ahlquist, MD, a Mayo Clinic gastroenterologist and co-inventor of the test said, “This study is further evidence that Cologuard is highly sensitive in detecting both early stage colorectal cancer and the most advanced precancerous polyps that are most likely to develop into cancer. A sensitive screening test like Cologuard that is delivered to a patient's home provides an opportunity to reverse that trend not only in Alaska but also in other rural and remote areas where patients have limited access to screening.” The study was published on October 28, 2015, in the journal Mayo Clinic Proceedings.

Related Links:
Alaska Native Epidemiology Center 
Mayo Clinic 
Exact Sciences Corporation