Unprecedented detection rates achieved with noninvasive colorectal cancer screening tool
Results of a clinical trial of a noninvasive, multitarget, stool DNA test showed unprecedented rates of precancer and cancer detection by a noninvasive test. The detection rates are similar to those reported for colonoscopy.
The test, known as Cologuard, is a noninvasive sDNA test for the early detection of colorectal precancer and cancer. It is based on a stool sample that is analyzed for DNA signatures of precancer or cancer. The samples are easily collected and mailed from home. They require no bowel preparation, medication restriction, or diet change. Cologuard was co-developed by the Mayo Clinic in Rochester, Minnesota, and by Exact Sciences.
The clinical trial, called the DeeP-C study, included 10,000 patients and was designed to determine how well Cologuard detects precancer and cancer. The study also compared Cologuard to the fecal immunochemical test for occult blood (FIT). The study was conducted at 90 medical centers throughout the United States and Canada. The results were published in the New England Journal of Medicine (2014; doi:10.1056/NEJMoa1311194).
"Cologuard detection rates of early stage cancer and high-risk precancerous polyps validated in this large study were outstanding and have not been achieved by other noninvasive approaches," said the study's author, David Ahlquist, MD. "It is our hope that this accurate and user-friendly test will expand screening effectiveness and help curb colorectal cancer rates in much the same way as regular screening, including genetic testing, has done for cervical cancer."
In the study, all patients received Cologuard, FIT, and colonoscopy. Colonoscopy was the reference method. The study found that Cologuard had an overall sensitivity of 92%, and 94% for the earliest and most curable cancer stages (stages I and II). Its sensitivity was 69% for precancerous polyps at greatest risk to progress to cancer (ie, those containing high-grade dysplasia). Also, Cologuard detected significantly more cancers and significantly more precancerous polyps than did FIT.
"The most important finding of the study is the high sensitivity of Cologuard for curable-stage colorectal cancer, which represents the highest sensitivity of any noninvasive test to date," said study author Thomas Imperiale, MD, a Professor of Medicine at Indiana University Medical Center in Indianapolis. "It is also significant to note that these results were achieved in a robustly conducted multicenter study."
Colorectal cancer is often considered the most preventable, yet least prevented, cancer. Nearly 50% of adults 50 years and older have not been screened as recommended and, as a result, colorectal cancer has become the second-leading cause of cancer death in the United States. Colorectal cancer is highly treatable if found early, and it is preventable if the precancerous polyps at greatest risk of progressing can be detected.
Cologuard works by testing a patient's stool for altered DNA shed during digestion and for the presence of blood. Combining this data provides a comprehensive, powerful screening approach. Because of its accessibility and ease of use, researchers hope the test will increase the number of people who will choose to be screened for colorectal cancer.