Blood Test Shows 83% Accuracy for Detecting Colorectal Cancer

Colorectal cancer is the second biggest cause of cancer deaths among adults in the U.S., with forecasts suggesting 53,010 people might die from it in 2024. While fewer older adults are dying from this cancer, the death rates for people under 55 have been going up by about 1% each year since the mid-2000s. Currently, it is recommended that people who are at an average risk for this type of cancer start getting checked regularly starting at age 45. Catching this cancer early through screening can make a huge difference, but only about half to three-quarters of people who should get screened actually take those tests. Now, a new study has found that a blood test can accurately detect colorectal cancer in 83% of individuals confirmed to have the disease, offering a new way for more people to get screened during regular doctor visits.

These findings are from the ECLIPSE study, a multisite clinical trial involving almost 8,000 people ages 45 to 84, led and funded by Guardant Health (Palo Alto, CA, USA). The study tested the effectiveness of Guardant’s Shield blood test against colonoscopies, the best screening method presently available. The Shield test works by detecting colorectal cancer signals in the blood that come from DNA shed by tumors, known as circulating tumor DNA (ctDNA). This ctDNA is also used in tests called “liquid biopsies” for monitoring cancer recurrence in patients who have already been treated and for other new cancer screening tests.

Image: The study showed the blood-based cancer screening test detects 83% of people with colorectal cancer with specificity of 90% (Photo courtesy of Guardant Health)

Out of the 7,861 participants reported in the study, 83.1% of those who had colorectal cancer confirmed through a colonoscopy also tested positive for ctDNA. Meanwhile, 16.9% had a negative ctDNA test, meaning the blood test did not detect their colorectal cancer. The blood test was particularly effective at detecting actual colorectal cancers, including those at an early stage, but was not as good at spotting advanced precancerous growths that could eventually become cancerous. The test's accuracy for detecting colorectal cancer was found to be similar to that of at-home stool tests that are also used for early detection.

“The results of the study are a promising step toward developing more convenient tools to detect colorectal cancer early while it is more easily treated,” said corresponding author William M. Grady, MD, a gastroenterologist at Fred Hutchinson Cancer Center. “The test, which has an accuracy rate for colon cancer detection similar to stool tests used for early detection of cancer, could offer an alternative for patients who may otherwise decline current screening options."

“We believe the publication of the ECLIPSE study in The New England Journal of Medicine, one of the world’s leading medical journals, is an endorsement of the quality of our clinical data and the potential value of the Shield test,” said AmirAli Talasaz, Guardant Health co-CEO. “We are confident that offering an accurate blood test has the potential to significantly reduce preventable colorectal cancer deaths.”