Colorectal cancer is the second-leading cause of cancer-related death in the United States. A 2026 American Cancer Society (ACS) report shows colorectal cancer rates are declining for individuals over the age of 65 but rising in younger adults. 

The importance of screening cannot be overstated. Many people are not current on colorectal cancer screening for a variety of reasons. Unfortunately, individuals who are not up to date on colorectal cancer screening are disproportionately impacted by colorectal cancer.

Screening guidelines recommend starting at age 45 for people at average risk. 

While a colonoscopy remains the standard for detection and prevention of colorectal cancer, there are alternatives. The ACS has recently released guidelines regarding a new blood test called Shield for people at average risk.

The Shield test: What you need to know

Shield is currently the first and only FDA-approved blood test for colorectal cancer screening. It looks for signs of cancer by testing a blood sample for changes that may suggest the presence of cancer cells. 

Who is a candidate for the Shield test?

The Shield test is only appropriate for people at average risk who cannot, or will not, undergo a colonoscopy or a stool-based test.

“If you do not plan to screen for colorectal cancer by another method, the Shield test is an FDA-approved screening option to discuss with your primary care provider,” says colon and rectal surgeon Matthew Fuglestad, MD. “However, a direct visualization exam such as screening colonoscopy remains the gold standard for both colorectal cancer screening and surveillance.”

The test is not recommended for people at high risk due to:

• A family history or personal history of pre-cancerous polyps or colorectal cancer.
• Hereditary conditions such as Lynch syndrome and familial adenomatous polyposis.
• A personal history of inflammatory bowel disease (IBD) such as ulcerative colitis or Crohn’s disease.
• Symptoms such as rectal bleeding, abdominal pain, or obstructive symptoms require a diagnostic colonoscopy.
• A personal history of radiation to the abdomen or pelvic area for prior cancer treatment.

This test is also not appropriate for monitoring recurrence after colorectal cancer treatment.

Pros:

• No bowel prep, fasting, or medication changes are needed.
• Non-invasive, with no sedation or downtime.
• The blood draw can be completed at your doctor’s office, with results available within one to two weeks.
• No direct risk to the colon.
• Effective at detecting stage 2, 3, and 4 colorectal cancers.

While convenient, Shield has some significant limitations that impact early detection and prevention. The ACS notes that blood-based screening tests are not currently preferred due to poor detection of precancerous growths.

Cons:

• Will only detect if you have – or don’t have – colon cancer. It is not effective at detecting pre-cancer or early-stage cancer.
• A positive test result requires a colonoscopy as the next step. 
• Low sensitivity of detecting pre-cancerous polyps (13%) compared with colonoscopy (93 to 95%).
• Misses approximately 40% of stage 1 cancers.
• Insurance may not cover the test.
• Screening needs to be repeated every three years.

Discuss your best-fit screening options with your doctor

“As a primary care physician, I am happy to discuss this new blood-based screening test with my patients,” says Stephen Mohring, MD. “It's important to have a conversation about both the benefits and the limitations of each screening method. Although the detection rate pales in comparison to colonoscopy and stool-based tests, it could be an option for patients unable to undergo any other form of screening.”

Early detection can increase survival by allowing for earlier and potentially less invasive treatment options. Estimates show that patients who were diagnosed with early-stage colorectal cancer have better survival outcomes.

Screening for colorectal cancer is safe, effective, and an important part of one’s overall health journey. Depending on your goals and values, there are a variety of methods available for screening. Whether you choose colonoscopy, a stool-based test, or a blood-based test, screening is a crucial step you can take that could save your life.

“It’s important to understand that the Shield test is an alternative to, but not a replacement for a colonoscopy,” adds Dr. Fuglestad. “If you're going to screen this way, it is important to talk with your doctor about its limitations and to ensure that you meet criteria for screening with Shield. For the best results from both a diagnosis and prevention perspective, a screening colonoscopy is still the way to go.”