Screening for Colorectal Cancer With One Blood Draw: cfDNA Test Has 83% Sensitivity for Colorectal Cancer

Many people who are eligible for colorectal cancer screening put off colonoscopy or stool tests. Professor Daniel C. Chung of Massachusetts General Hospital in the United States and colleagues published in NEJM the ECLIPSE study, which evaluated the performance of a colorectal cancer screening test that analyses cell-free DNA (cfDNA) in the blood. A blood test has been expected to raise screening participation because it requires only a blood draw.

A Diagnostic Accuracy Study Using Colonoscopy as the Reference

This study is a diagnostic accuracy study, not a drug trial, so it has no clinical trial phase. It enrolled 10,258 average-risk adults eligible for screening and compared the blood test results of the 7,861 who met the criteria with colonoscopy findings. The co-primary endpoints were sensitivity for colorectal cancer and specificity for advanced neoplasia (colorectal cancer or advanced precancerous lesions).

The blood test returned a positive result for 83.1% of colorectal cancers confirmed by colonoscopy, and 87.5% of stage 1 to 3 colorectal cancers. Of people without advanced neoplasia, 89.6% tested negative, meaning about 10% were false positives. Sensitivity for advanced precancerous lesions, however, was only 13.2%. There is no procedural risk beyond the blood draw, but a false-positive result requires a follow-up colonoscopy.

Significance and Limits

It could be an alternative for people who avoid colonoscopy, but it is hard for it to replace the role of colonoscopy in preventing cancer by finding and removing polyps. The test's developer (Guardant Health) funded the study, and the actual effect on reducing mortality and the appropriate testing interval must be verified separately.