A New Blood Test to Screen for Colorectal Cancer Shows Promise

Fact checked by Nick Blackmer

Key Takeaways

• A new, noninvasive colorectal cancer test can detect cancer and pre-cancers with a blood sample.

• According to early data shared by the manufacturer, the test is on par with, if not better than, currently available stool tests.

• Colonoscopies remain the gold standard for detecting and preventing colorectal cancer.

A new screening test can detect colorectal cancer with a simple blood draw in people with an average risk of the cancer.

The test can detect early-stage colorectal cancer with a sensitivity of 93%, according to mid-stage data shared by the test maker, Universal DX, in May. The test can also detect the pre-cancerous growths with 54% sensitivity.

Colonoscopies are the gold standard for colorectal cancer screening. Not only can a provider find and diagnose cancerous growths, but they can also remove pre-cancerous polyps.

However, colonoscopies require a visit with a physician and a couple days of preparation before the procedure, which may discourage them from getting routine testing. Providers will sometimes recommend non-invasive screening tests, such as Cologuard and FIT tests, for people without family history of colorectal cancer.

Related: When Should You Get Screened for Colon Cancer?

The new blood-based test, called Signal-C, appears to be as accurate or more accurate than most sample-based screening tests.

Anaum Maqsood, MD, an oncologist at Houston Methodist Hospital, said that while she will continue to rely on colonoscopies for accurate detection and prevention of colorectal cancer, the blood test is “very promising.”

“The challenge comes when we have patients who don’t want to take the colonoscopy,” she told Verywell. “Perhaps they don’t want to undergo that extensive two-day prep and a procedure. Then there are some patients who are on blood thinners where a colonoscopy is technically challenging. That’s when we have to look for alternatives like Cologuard, and now the Universal DX test.”

The company is launching a pivotal trial including about 15,000 patients next month and will seek FDA approval if it’s successful.

Colorectal Cancer Screening Recommendation

The U.S. Preventive Services Task Force (USPSTF) recommends that adults ages 45 to 75 be screened for colorectal cancer, and that adults older than 75 consult with a doctor about further screening. Colonoscopies are recommended every 10 years for people with average cancer risk, while noninvasive screening types may be used annually.

How the Blood Test Works

During its lifespan, a cancer cell sheds parts of its DNA into the bloodstream. Researchers can link these fragments of genetic code to certain types of cancer. When these so-called biomarkers show up in a blood sample, it may be a sign of early cancerous growths.

To complete the Signal-C test, patients will get a blood draw at their annual physical or at a local lab. The sample is sent to the company’s lab, where they analyze it for early signs of cancer or adenomas using tools including a machine learning model.

The company will report back a positive or negative result. People with a positive test should schedule a colonoscopy, while those with a negative result can await their next screening, Kristi Kruusmaa, MSc, PhD, Chief Scientific Officer at Universal Diagnostics, told Verywell.

To test the screening tool, researchers analyzed blood samples from nearly 1,000 patients in the U.S. and Europe. The participants received a colonoscopy or colonic surgery for primary colorectal cancer soon after. The researcher compared the results from the blood test to the cancer and pre-cancers detected during the procedures.

The test had a specificity of 93% for cancer detection, meaning there’s a 7% chance that a patient receives a false positive result. The test was more accurate for people with late-stage disease than early-stage disease, according to data presented at the Digestive Diseases Week conference. Kruusmaa said that patients who receive a false positive often have some benign finding, such as a small polyp or previously undiagnosed gastrointestinal disease.

A Step Closer to Detecting Pre-Cancers, But Not Quite There Yet

Colorectal cancers often develop from benign tumors called adenomas. While most of these growths remain harmless, some become malignant. Clinicians usually consider an advanced adenoma to be a precursor to cancer and have them removed.

The Signal-C test catches advanced adenomas in about 54% of the tests. That’s better than Cologuard, which is about 42% accurate, and most FIT tests, which are around 24% accurate.

“That pre-cancer detection is absolutely crucial because when you detect those patients, you send them to colonoscopy, and you are preventing cancer,” Kruusmaa said.

While Signal-C appears more sensitive at detecting precancerous growths than stool tests, Maqsood said she will continue to recommend colonoscopy for detecting advanced adenomas. When experienced providers perform colonoscopies, they tend to correctly identify advanced adenomas in 89% of patients.

“[Colonoscopy] is not just diagnostic, it’s also therapeutic,” Maqsood said. “The lesion never gets a chance to become a cancer. That’s how we will decrease cancer incidence.”

Related: How Colon Cancer Is Diagnosed

A Blood-Based Test Expands Screening Options

Colonoscopies require patients to do some prep-work. This often includes a period of fasting, drinking a liquid laxative to clear the bowels, and stopping certain medications before the procedure.

Some people may opt for a blood-based screening test over a routine colonoscopy due to the discomfort associated with the procedure. Others may choose it for the convenience.

“I’m in Houston, Texas, but there are remote areas of east Texas, west Texas, and in the valley, where we don’t have enough physician coverage and we don’t have enough people who are doing their colonoscopy on a regular basis,” Maqsood said. “I think it would be a good idea to target those people who don’t have regular access to care.”

Kruusmaa said Universal DX considered creating a test that screens stool and urine samples, but they found that people were most comfortable submitting blood.

“Even the best organized screening programs don’t manage to really convince people to take part, because they don’t want to deal with stool samples,” Kruusmaa said.

Besides, only certain kinds of cancers can be detected in a stool sample, while it’s possible to find cell free DNA from most cancer types in blood. Developing a colorectal cancer blood test could lay the groundwork for other, more universal cancer tests.

What This Means For You

Colorectal screening tests may not be right for every patient. Speaking with a healthcare provider can help you understand the best way to screen for the cancer based on your age, family history, and other risk factors.