New colon cancer blood test does not replace colonoscopies

September 9, 2024

Swedish Health Team

[4 MIN READ]

The U.S. Food and Drug Administration (FDA) has approved a new blood test that detects colorectal cancer, which is rising among Americans 50 and younger.
The new blood test should not replace colonoscopies, which remain the gold standard in colorectal cancer screening and prevention.
Colonoscopies detect precancerous polyps that can be removed on the spot, while the new blood test only detects cancer once it begins to form.

New blood test for colon cancer does not replace colonoscopies

Colorectal cancer rates are rising among younger adults. The American College of Surgeons (ACS) reports that since 2004, there has been a 15% increase in colorectal cancer diagnoses of people between the ages of 18 and 50. It's a concerning trend, as colorectal cancer is now the leading cause of cancer-related deaths in men younger than 50 and the second-leading cause of cancer deaths in women of the same age.

Still considered the gold standard for colorectal cancer prevention and screening, the ACS recommends annual colonoscopies starting at age 45. However, the U.S. Food and Drug Administration (FDA) recently approved a new colorectal cancer test that only requires a blood sample to detect cancers in their earliest stage, when they may be more curable.

With the accessibility of a simple blood test for colon cancer, some patients may wonder if they still need regular colonoscopies. To clarify the issue, we spoke with Rodney Kratz, M.D., a colon and rectal surgeon at the Swedish Cancer Institute and the Swedish Digestive Health Institute.

Blood tests detect, colonoscopies can prevent

The FDA approval of the new colon cancer blood test makes it the first blood test approved for the primary screening of colorectal cancer in people 45 and older. It also meets coverage requirements for Medicare reimbursement.

While some people consider a routine blood test a less-complicated alternative to a colonoscopy, the Shield test cannot detect precancerous growths that colonoscopies can. During a colonoscopy, doctors can also remove those growths to prevent cancer from growing.

“It is important that patients understand that the Shield test only detects cancer,” says Dr. Kratz. “And that is something we never want to do. We want to prevent cancer altogether, and colonoscopies remain the only option for that.”

Studies found the new test to be 83% effective in finding colorectal cancers through trace cancer DNA in the bloodstream. It needs to be taken at least every three years, starting at age 45, the same age the American Cancer Society recommends beginning colorectal screening.

If the test detects cancer, you’ll need a colonoscopy

Some people avoid colonoscopies because the procedure can require up to a day of fasting as well as taking a powerful laxative to clean out the colon. Colonoscopies also require anesthesia, which may mean missing work and finding a ride home after the procedure. Other people don’t like fecal tests that require collecting and mailing stool samples to a lab for testing.

With as many as 53,000 Americans expected to die from colorectal cancer this year, the hope is that the blood test can encourage more people to ask for a screening. Early detection is key, and this is why — despite its inability to prevent colon cancer — the FDA committee recommended approving Shield. It might encourage more people to get colonoscopies.

However, even with blood tests, colonoscopies cannot be avoided entirely. If a test detects colorectal cancer or a large polyp, only a colonoscopy can find and remove the problem.

“There's only one method of removing polyps and that is a colonoscopy,” says Dr. Kratz. “The Shield test is a newly FDA-approved blood test for the potential detection of colorectal cancer. It does not play any role in preventing it.”

Colonoscopies catch and remove precancerous polyps

Colorectal cancer forms when small, noncancerous groups of cells called polyps form in the lining of the colon or rectum. Some of these polyps are harmless, but others grow and develop into cancer.

The best prevention for colorectal cancer is to remove any polyps as soon as possible. Polyps that remain may become cancerous, grow and then spread to other organs, like the liver.

Most cases of colorectal cancer are preventable, and treatments are most effective when the cancer is found early. Colonoscopies allow doctors to find polyps early and remove them either before they develop into cancer or at the earliest stage possible.

“We really want to prevent cancer or catch it early, and if we catch it early, we have a better chance of successfully treating it,” says Dr. Kratz.

The American Cancer Society recommends that people get their first colonoscopy at age 45. After that, they should have a colonoscopy every 10 years until at least 75, unless there are other risk factors.

Colorectal cancer risk factors include:

A family or personal history of colorectal cancer or polyps.
Eating a lot of red meat.
Excessive alcohol consumption.
Genetic syndromes, such as Lynch syndrome or familial adenomatous polyposis.
Inflammatory bowel disease.
Obesity or being overweight.
Smoking.

Dr. Kratz recommends that patients with these risk factors talk to their providers, who can advise them on whether to start colonoscopies at a younger age or have them more frequently.

Colonoscopies can find cancer at the earliest stages

Treatment plans for colorectal cancer are determined by the stage of cancer, the size of the tumor and where the tumor is located. Surgery is the most common treatment, but it isn’t always the right course of action due to age and other health conditions.

Cancerous polyps that have not yet spread may be surgically removed with a colonoscope — a long, flexible tube and camera that the surgeon uses during a colonoscopy. This procedure is called a polypectomy.

More advanced colorectal cancer may require additional treatments and procedures. These may include radiation and chemotherapy before or after surgery.

Learn more and find a provider

If you’re 45 or older or you have a family history of colon cancer, talk to your doctor about colorectal cancer screenings. Whether you require an in-person visit or want to consult a doctor virtually, you have options. Contact Swedish Primary Care to schedule an appointment with a primary care provider. You can also connect virtually with your provider to review your symptoms, provide instruction and follow up as needed. And with Swedish ExpressCare Virtual you can receive treatment in minutes for common conditions such as colds, flu, urinary tract infections and more. You can use our provider directory to find a specialist or primary care physician near you.

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