Blood test can detect colorectal cancer with 83% accuracy, study says

One new blood test developed for the colorectal cancer screening (or bowel cancer) correctly detected the tumor in 83% of people who had been diagnosed with the disease. The discovery suggests that the test could be a new option for early cancer diagnosis.

The findings were displayed in a study published on the 14th in the The New England Journal of Medicine. The test's accuracy rate is similar to stool tests used to detect colorectal cancer.

“The study results are a promising step toward developing more convenient tools to detect colorectal cancer earlier while making it more easily treated,” says study corresponding author William M. Grady, a gastroenterologist at the Fred Hutchinson Cancer Centerin Seattle, in the United States.

“The test, which has an accuracy rate for detecting colon cancer similar to stool tests used for early diagnosis, may offer an alternative for patients who might otherwise decline current screening options.” complete in a press release.

To arrive at the findings, the researchers used the ECLIPSE study, a clinical trial carried out with almost 8 thousand people aged between 45 and 84 . This study compared a blood test called Guardian's Shield with colonoscopy, which is the gold standard procedure for colorectal cancer screening today.

The exam Guardian's Shield detects signs of bowel cancer in the blood from DNA that is shed by tumor cells, called circulating tumor DNA (ctDNA ).

Some study participants already had a diagnosis of colorectal cancer confirmed by colonoscopy. Of these, 83.1% underwent a blood test and presented a positive result for ctDNA and 16.9% had a negative test. The test was more sensitive for early-stage and advanced colorectal cancer, and was less sensitive for advanced precancerous lesions, which can transform into cancer over time.

For Grady, the sensitivity of the blood test for colorectal cancer is similar to stool tests, but lower than that of colonoscopy, which, for him, It is still the most accurate screening test for tumors .

“Colorectal cancer is common and very preventable with screening, but only about 50% to 60% of people eligible for screening actually get these tests,” says Grady, who is medical director of Fred Hutch's Gastrointestinal Cancer Prevention Program. “Getting people screened for cancer works best when we offer screening options and then let them choose what works best for them.”

In the United States, where the study was carried out, colorectal cancer is the second most common cause of cancer death in adults and is expected to be responsible for more than 53 thousand deaths in 2024, according to American Cancer Society. In Brazil, the estimated number of new cases of this cancer is 45,630 cases for each year of the three-year period 2023-2025 according to Inca (National Cancer Institute).

Current guidelines recommend that screening for colorectal cancer be done regularly from 45 years old.

“We continue to see younger people getting colorectal cancer, and it is now the third most common cancer in people under 50,” says Grady. “Having a blood test for people to do during routine doctor visits could be an opportunity to help more people get screened.”