The colon or rectum is where colorectal cancer begins. The large intestine stores the leftover waste until it can be expelled during a bowel movement.

According to the American Cancer Society (ACS), CRC is the third most common type of cancer in the United States. It’s also the third-leading cause of cancer death, making early detection and treatment very important.

A colorectal cancer screening can include a colonoscopy or stool-based tests. A less-invagant blood test can be used to look for colorectal cancer. This test is not standard yet in screening.

In this article we will look at blood-based tests, how they may be used for the purpose of screening for colorectal cancer, and what the current guidelines say.

A blood-based test looks for signs of cancer in the body. It uses a sample of blood from your arm to do this.

Cancer-specific markers are basically anything that’s made by cancer cells or produced by your body in response to cancer. They often include proteins or specific changes related to nucleic acids (DNA or RNA).

Looking for these markers can help inform a doctor.

  • Does cancer exist?
  • If specific treatment types are more effective.
  • How well a current cancer treatment is working?
  • Estimates of the outlook for cancer.

How are blood-based biomarkers used now?

For the most part, blood-based biomarker tests are currently used more for treatment and outlook purposes than for screening. An example of this is the CA-125 blood test, which is sometimes used for ovarian cancer.

CA-125 is made by ovarian cancer cells and can be present in the blood. A drop in CA-125 levels can indicate that a treatment is working. However, an increase can point to an ineffective treatment or a cancer recurrence after remission.

“It is important to note that blood biomarker tests aren’t typically used by themselves. Other tests are needed to support the results.”

If the CA-125 levels rise, it may be a sign of a potential ovarian cancer reappearance. A doctor will still want to do tests to get a better idea of what is going on.

What about using blood-based biomarkers for screening?

The use of blood-based biomarkers in colorectal cancer screening is still in its early stages. According to the National Cancer Institute, there are still some hurdles to overcome.

Sensitivity and specificity are what these have to do with. A test for cancer screening should be both sensitive and specific.

A test with high sensitivity will detect cancer in most people, but a test with low sensitivity will not pick up on everyone. If cancer is present, more screening tests may be needed.

A test with high specificity will find cancer biomarkers specific to a specific type of cancer. You may get more false positives when specificity is low. This can lead to more testing.

There’s currently one blood-based biomarker test for colorectal cancer screening that’s been approved by the Food and Drug Administration (FDA). It’s called the Epi proColon test and was approved in 2016.

The Epi proColon test uses a blood sample to look for a specific change to DNA called methylation. Methylation is a type of change to your DNA that can regulate how a gene is expressed.

This test is specifically looking for methylation in a certain area of a gene called Septin 9 (SEPT9). The presence of methylation here is associated with CRC.

When is the Epi proColon test used?

“The Epi proColon test is used for screening for colorectal cancer in people who are at an average risk level. It isn’t meant to replace standard screening tests.”

The manufacturer of the test states that typical CRC screening tests should be offered and declined prior to using the Epi proColon test. Further, they note that a diagnostic colonoscopy is still necessary after a positive Epi proColon result.

How accurate is the Epi proColon test?

An early study of the Epi proColon test was carried out in 2014. The test’s overall sensitivity was 48.2%. However, specificity was higher at 91.5%.

Another 2014 study compared the Epi proColon test with another biomarker test for CRC that uses a stool sample. It found that the Epi proColon test had comparable sensitivity to the stool test, but its specificity was much lower.

A 2019 review noted that the Epi proColon test may increase CRC screening in people who decline screening by colonoscopy.

Concerns were raised that some people may opt for Epi proColon instead of other screening tests. Some of theCRCs that could have been found using other methods may be missed because Epi proColon has lower sensitivity.

CRC is increasing in younger people. As such, a 2022 study looked into Epi proColon as a less invasive way to screen for early-onset CRC. The researchers found that the test was quite sensitive and specific for this purpose.

Is the Epi proColon test covered by insurance?

The Epi proColon test is covered by some types of insurance. If you ever doubt whether a particular test is covered by your insurance, it is a good idea to check with your provider.

For example, Medicare states that they’ll cover an approved blood-based biomarker screening for CRC once every 3 years.

However, the Centers for Medicare and Medicaid Services (CMS), which administers Medicare, has said that the Epi proColon test doesn’t meet its sensitivity and specificity criteria for coverage.

How else are blood-based biomarkers used in colon cancer?

There are several additional markers that may be used for colorectal cancer. Similar to what we have covered before, many of these are discussed in relation to treatment and outlook.

A 2019 review summarizes these biomarkers at length. Let’s have a brief look at a couple of these biomarkers.

  • Circulating tumor cells. Circulating tumor cells are cancer cells that are in the bloodstream. Generally speaking, circulating tumor cells are associated with poorer CRC outlook. Their presence may be an indicator that the cancer has spread beyond the large intestine to distant organs like the liver, lungs, or brain.
  • Tumor DNA. Tumor DNA in the blood can also be analyzed for certain changes, as in the Epi proColon test. Some of the changes, like those in the genes KRAS and BRAF, can indicate that a CRC may be resistant to certain treatments.

Scientists and doctors are working to find new markers for colorectal cancer. They are looking to improve strategies to detect and measure the CRC.

Two newer types of blood-based markers forCRC are long noncodingRNA andmiRNA.

  • miRNA: These are small strands of RNA that can play a role in controlling the types of proteins cells make. They can sometimes be found in the bloodstream. Research has documented changes in the levels of certain miRNAs in CRC compared with healthy individuals.
  • lncRNA: These are longer strands of RNA that can also sometimes be found in the blood. lncRNAs can also play a role in regulating how genes are expressed. A 2022 review notes that many lncRNAs have been associated with all stages of CRC.

Researchers are hoping to learn more about how these molecules are associated with different aspects of the project.

Blood-based biomarkers aren’t just used for CRC. They’re also being investigated for cancers of the lung, breast, and more. In fact, they’re even being looked at for early detection of Alzheimer’s disease.

When most cancers are detected and treated early, the outlook is greatly improved. Regular screenings are vital in the case of CRC.

“When should you have a screening? What tests can you take? Let’s look at some of the guidelines.”

Both the U.S. Preventive Services Task Force and the ACS recommend that adults ages 45 to 75 who are at average risk be screened for CRC. The currently recommended screening test options include:

The Epi proColon test is not recommended for screening.

Blood-based markers are used to assess cancer treatment. Their use in cancer screening is limited at the moment.

There is a FDA-approved blood-based test for the disease. It is not recommended as a part of standard screening guidelines because of its sensitivity and specificity.

Colorectal cancer is the third-leading cause of cancer death in the United States. As such, talk with your doctor about your CRC risk level and when you should start screening. They can also recommend which screening tests would be a good fit for you.