New cfDNA Blood Test Detects Colorectal Cancer but Limited in Detecting Advanced Precancerous Lesions

Colorectal cancer (CRC) is the second leading cause of cancer-related deaths in the U.S. Screening for CRC in average-risk individuals between the ages of 45-75 is vital to decreasing the morbidity and mortality from this potentially deadly disease. There are many screening options available, including the new cfDNA test that was the focal point of a recent study in the New England Journal of Medicine (NEJM). We must provide patients with the best information to make the appropriate decisions regarding screening options.

As the study demonstrated, the performance of the cfDNA blood test for detecting CRC is acceptable at 83.1% sensitivity. It has the potential to improve overall patient adherence to screening. However, the cfDNA test detected only 13% of advanced precancerous lesions. Colonoscopy detects more than 90% of advanced precancerous lesions, and thus can prevent colorectal cancer rather than just detect it. The new cfDNA test is also less effective than currently available fecal tests for detecting advanced precancerous lesions. Identifying and removing advanced precancerous lesions is critical to preventing CRC.

We recognize that not all patients have access to or are willing to undergo colonoscopy. However, patients should be offered colonoscopy or a stool-based test and decline those before they are offered a blood-based test that cannot detect precancerous lesions well. Patients who undergo a stool-based CRC screening test or a blood-based test must undergo colonoscopy if that test is positive. Further, it is not clear that this test will be cost-effective relative to current tests.

Advances in technology may improve the cfDNA blood-based detection of advanced precancerous lesions in the future; at this time, it has several limitations. It is important to clarify and educate clinicians on the importance of sequential offers of screening tests. In particular, the availability of the cfDNA test should be accompanied by recommendations for colonoscopy and the currently available fecal tests first, reserving the cfDNA test for patients who decline colonoscopy and fecal testing as well as understand the limitations of the cfDNA test.

About Gastrointestinal Endoscopy
Gastrointestinal endoscopic procedures allow the gastroenterologist to visually inspect the upper gastrointestinal tract (esophagus, stomach and duodenum) and the lower bowel (colon and rectum) through an endoscope, a thin, flexible device with a lighted end and a powerful lens system. Endoscopy has been a major advance in the treatment of gastrointestinal diseases. For example, the use of endoscopes allows the detection of ulcers, cancers, polyps and sites of internal bleeding. Through endoscopy, tissue samples (biopsies) may be obtained, areas of blockage can be opened and active bleeding can be stopped. Polyps in the colon can be removed, which has been shown to prevent colon cancer.

About the American Society for Gastrointestinal Endoscopy
Since its founding in 1941, the American Society for Gastrointestinal Endoscopy (ASGE) has been dedicated to advancing patient care and digestive health by promoting excellence and innovation in gastrointestinal endoscopy. ASGE, with almost 16,000 members worldwide, promotes the highest standards for endoscopic training and practice, fosters endoscopic research, recognizes distinguished contributions to endoscopy, and is the foremost resource for endoscopic education. Visit and for more information and to find a qualified doctor in your area.


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