• Posted March 14, 2024

Colon Cancer Blood Test 83% Accurate in Spotting Tumors

An experimental blood test accurately detected colon cancer in more than 8 in 10 people confirmed to have the disease, researchers report.

The test -- which could be an option for people who want to avoid colonoscopy -- is intended for people who have no colon cancer symptoms and are at average risk.

"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 Dr. William Grady, a gastroenterologist at Fred Hutchinson Cancer Center in Seattle. 

Current guidelines recommend regular screening starting at age 45. But only 50% to 60% of people who are eligible for colon cancer screening actually take the tests, Grady said.

"Having a blood-based test for people to take during routine doctor's visits could be an opportunity to help more people be screened," he said in a Fred Hutchinson news release.

More than 7,800 people between the ages of 45 and 84 participated in a multisite clinical trial of the new blood test. The research was funded by Guardant Health, developer of the Shield blood test.

The test detects colon cancer signals in the blood from DNA shed by tumors. Called circulating tumor DNA, or ctDNA, it is also used to monitor for recurring cancer and in other emerging screening tests.

In all, 83% of study participants with confirmed colon cancer tested positive for ctDNA. Seventeen percent had a negative test, meaning the blood test did not show colon cancer even though a colonoscopy did. 

Researchers said the test was most sensitive for colon cancers, including those in the early stages, and less sensitive in detecting lesions that could become cancerous.

The findings were reported March 14 in the New England Journal of Medicine.

Grady likened the blood test's sensitivity to that of stool-based tests. But he said it is lower than that of colonoscopy, which he considers the most accurate colon cancer screening tool.

"Getting people to be screened for cancer works best when we offer them screening options and then let them choose what works best for them," he said.

Colon cancer is the second leading cause of cancer deaths in U.S. adults, according to the American Cancer Society. It projects that over 53,000 people will die of the disease this year.

While death rates from the disease have dropped among older adults, rates among people under 55 are on the rise. They have risen about 1% a year since the mid-2000s.

"We continue to see younger people getting colorectal cancer, and it's now the third most common cancer for people under the age of 50," Grady said.

More information

The U.S. Centers for Disease Control and Prevention has more about colon cancer screening tests.

SOURCE: Fred Hutchinson Cancer Center, news release, March 14, 2024