FDA Approves First Blood Test to Detect Colorectal Cancer

A blood test that can detect colorectal cancer — the third most diagnosed cancer in the United States — will be available for adults 45 years and older who are at average risk for developing the disease, such as those without a personal or family history of colorectal cancer. People can get the test done during routine visits to their healthcare providers, with results ready in around two weeks.

Developed by Guardant and marketed as Shield, the blood test is the first to be approved by the Food and Drug Administration (FDA) as a primary screening option for colorectal cancer. Following its approval, Medicare also announced that it would cover the test.

“The test can signal disease through identifying cancerous DNA from tumors that make their way into the bloodstream,” says Dr. Joel T. Gabre, a gastroenterologist at NewYork-Presbyterian/Columbia University Irving Medical Center. “However, it’s important for patients to understand that a colonoscopy, the gold standard for colorectal cancer screening, allows us to both detect and remove precancerous lesions, such as polyps, in the colon, which is a big difference from a blood test.” For those who decide to take the blood test and get a positive result, a colonoscopy is recommended as the next step.

Most cases of colorectal cancer start as polyps in the colon or rectum, growths that are common as people get older and which are mostly benign or noncancerous, according to the American Cancer Society. But over time, some types can change into cancer.

Approval of the blood test follows a strong recommendation by an FDA-advisory committee in May 2024, who based their support on promising results from a study published in the New England Journal of Medicine in March 2024. The study evaluated almost 8,000 people who were at average risk for colorectal cancer and undergoing routine screening with colonoscopy.

“Results showed that in average risk patients, this blood test had an 83.1% sensitivity at detecting colorectal cancer,” says Dr. Gabre. “This means a little more than 8 in 10 patients in the study with colorectal cancer detected by colonoscopy also had a positive blood test. But when it came to polyps and advanced pre-cancerous lesions, the blood test was only 13.2% sensitive at detecting these types of lesions.”

Since the mid-1990s, colorectal cancer incidence has dropped in older adults, most likely due to adherence to screening and improvements in lifestyle factors. But cases have increased by 1% to 2% per year in the same time frame in people younger than 55 years of age.

While colorectal cancer is highly treatable if caught early, it is the leading cause of cancer-related death in adults, research shows. Early detection could prevent more than 90% of these deaths but one out of three people in the U.S. who are eligible for screening — over 50 million — are not up to date with screening. In 2021, the U.S. Preventive Services Task Force updated its guidelines to recommend everyone get screened for colorectal cancer starting at age 45, no matter their family history.

There are a variety of factors that contribute to patients not undergoing screening for colorectal cancer, which spans from patient-related factors, like fear of the procedure itself, all the way to healthcare system-related factors, such as access to screening tests and care coordination, explains Dr. Gabre. “Addressing all of these factors is important.”

“While the blood test is good at detecting cancer, it is not the same as a colonoscopy, which is better at identifying pre-cancerous growths like polyps,” adds Dr. Gabre. “For people who would not want a colonoscopy, however, the blood test provides patients with another option, which may contribute to improved screening rates. But it’s important for healthcare providers to explain the advantages and disadvantages of this test and other screening options for colorectal cancer.”

Dr. Joel T. Gabre sees patients in the Gastrointestinal Cancer Prevention and Genetics Program at NewYork-Presbyterian/Columbia University Irving Medical Center and runs a laboratory dedicated to understanding the molecular mechanisms of gastrointestinal tumors. Dr. Gabre is also an assistant professor of medicine at Columbia University Vagelos College of Physicians and Surgeons.