A Closer Look At The New Blood Test For Colon Cancer

The U.S. Food and Drug Administration (FDA) recently approved a blood test that can spot colon cancer. Sound too good to be true? In some ways, it is.

The FDA approved the test in July 2024 as a primary screening option for colon cancer. This means providers can offer it similarly to other noninvasive screening methods, which include stool-based tests. However, all noninvasive tests are less accurate than colonoscopy. Colonoscopy is the gold standard for screening people who are at average risk for colon cancer.

In a colonoscopy, the doctor examines the lining of the large intestine and rectum using a long, flexible tube with a light and tiny camera. During this test, doctors can remove precancerous polyps (growths). Removing these growths is the only way to prevent colon cancer before it even starts. About one-third of people who have a screening colonoscopy end up having at least one polyp removed during the procedure.

As effective as colonoscopy is for stopping colorectal cancer, many adults put this routine cancer screening off indefinitely.

"The blood test is by no means perfect, but it is certainly a better option than not getting screened at all," said Niraj Gupta, MD, a medical oncologist with Franciscan Physician Network in Carmel, Indiana. "The same can be said for stool-based tests. These tests detect hidden blood or abnormal genetic material in the stool, which are possible signs of colon cancer. But they aren’t as accurate as a colonoscopy either."

Dr. Gupta added that if a blood or stool-based test is positive, you will need a follow-up colonoscopy to help your care team learn more.

Concerns About The Colon Cancer Blood Test

The main issue with blood tests is that, unlike colonoscopies, they often miss precancerous growths on the colon. These growths, also called polyps, can be removed during a colonoscopy, potentially preventing colon cancer.

The blood tests detect 83% of colorectal cancers but only 13% of dangerous polyps. In contrast, colonoscopies find 95% of dangerous polyps, and the most advanced fecal test finds 42%.

Another disadvantage is cost. Although FDA-approved, the blood test costs hundreds of dollars. Medicare covers the cost. Other insurance plans may not cover the cost of this test yet, but may start covering it soon. Check with your insurance plan about coverage of blood tests for colorectal cancer screening.

The Importance Of Colorectal Cancer Screening

Colorectal cancer is the third-most common cancer in adults in the United States. It is the second-leading cause of cancer death.

"If everyone followed the American Cancer Society’s colon cancer screening recommendations, far fewer people in this country would get the disease or die from it," Dr. Gupta said.

The American Cancer Society recommends colorectal cancer screenings beginning at age 45 unless you have a family history of colorectal cancer or other risk factors for the disease.

If you are at higher risk for colorectal cancer, colonoscopy is the only recommended screening option. Talk to your primary care provider about starting screenings earlier. You may also want to discuss getting them more frequently than people at average risk.

Talk To Your Doctor About What’s Best For You

The new colon cancer blood test may be a good alternative for people who refuse to schedule a colonoscopy. But it isn’t as accurate, nor can it be used to remove precancerous polyps.

Your health is important. Talk to your primary care provider to see if you are due for a colon cancer screening. Ask what type is best for you.