New Blood Test Added for Colorectal Cancer Screening

For the first time, a blood test has been included in the American Cancer Society’s recommended screenings for colorectal cancer. This addition is not intended to replace colonoscopies, but rather to reach individuals who may otherwise skip screening altogether.

Dr. William Dahut, the chief scientific officer at the American Cancer Society, mentioned, “About a third of Americans are not up to date with colorectal cancer screening.” He suggested that introducing this new test could significantly increase the number of individuals screened, particularly since colorectal cancer is now the leading cause of cancer death in people under 50.

The blood test, known as Shield, was developed by Guardant Health in California and received approval from the Food and Drug Administration in 2024. It functions by detecting DNA fragments released by tumors. Notably, the American Cancer Society recommends it only for those who cannot or choose not to have more effective methods like colonoscopies or stool tests.

Studies indicate that the Shield blood test is about 83% effective in detecting colorectal cancers, though it excels at identifying more advanced stages rather than early signs, which are easier to treat. Precancerous polyps do not release these DNA fragments, and so far, there is no long-term data confirming the test’s ability to save lives.

“It won’t be as good at identifying precancerous areas or stage 1 cancers,” Dahut acknowledged, “but it’s certainly much better than not being screened at all.”

The new recommendations from the American Cancer Society were released recently; however, they don’t guarantee that insurance will cover the blood test. Insurance coverage usually follows guidance from the U.S. Preventive Services Task Force, which has not yet commented on this. The Shield test comes with an out-of-pocket cost of $895.

Dr. Scott Kopetz, a gastrointestinal oncologist at the University of Texas MD Anderson Cancer Center, expressed a mix of enthusiasm and concern regarding new colorectal cancer testing options. He indicated that while it’s positive to have more testing methods available, there’s a risk that people might rely too heavily on the blood test and mistake it for the gold-standard colonoscopy.

Kopetz stated, “This is better than nothing, for sure. The concern is that we’re going to lose ground in our battle for colorectal cancer prevention and early detection. This could lead to a decline in the quality of screening that patients could otherwise receive, simply because there’s a demand for something easier and quicker.”

Colorectal cancer cases are particularly rising among adults under 65, with over 108,000 new colon cancer cases and nearly 50,000 rectal cancer cases expected to be diagnosed this year in the U.S. The recommendation for average-risk individuals to start screening at age 45 remains unchanged.

Experts reaffirm that colonoscopy is the most effective screening tool available. This method involves inserting a small, flexible camera into the rectum and colon, which allows doctors to identify and remove potentially cancerous polyps.

Despite its effectiveness, colonoscopy is a two-day procedure often requiring time off work. Patients must prepare by adopting a liquid diet and taking laxatives a day prior to ensure the colon is clear for examination. The procedure itself is painless and performed under anesthesia, with a recovery requirement of having someone drive them home. Generally, colonoscopy screenings are recommended every ten years.

New guidelines also support the latest stool-based tests, such as Cologuard and ColoSense, which can be conducted at home or in a doctor’s office. These tests are performed every one to three years and involve collecting stool samples without any dietary restrictions or laxative prep.

The Shield blood test is even simpler but is recommended every three years. However, neither the blood nor stool tests can completely eliminate the need for a colonoscopy if results are positive, as a colonoscopy provides crucial information on tumor location and treatment options.

Dr. Kimmie Ng, who leads the Young-Onset Colorectal Cancer Center at Dana-Farber Cancer Institute in Boston, emphasized the importance of screening and reaching as many individuals as possible at risk for colorectal cancer. “Getting screened is more important than ever,” Ng stated. “Having a variety of options available encourages more people to get screened, which is really quite important.”