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Biomarkers

Explore our resources on biomarker testing

What are biomarkers?

Biomarkers are proteins present in or released by the tumor or metastases that can be detected in blood, other bodily fluids, or tissues.

Things you should know about biomarker testing

Which tests might be useful for me? A cheat sheet

MSS/MSI-H

All newly diagnosed CRC patients should have their tumors tested for MSS/MSI status. Finding out which kind of tumor you have can have a big impact on what treatment options are available to you.

So what do those acronyms really mean? Learning about mismatch repair (MMR) is a great place to start.

All patients who are diagnosed with stage IV metastatic CRC should have their tumor tested for RAS status. There are three different RAS family members (KRAS, NRAS and HRAS) that can be mutated in colorectal cancer.

BRAF

All patients diagnosed with colorectal cancer should have their tumors tested for BRAF status. BRAF mutations are found in 10-15% of CRC.

HER2/ERBB2

HER2 (also called ERBB2) amplifications/mutations are present in about 8% of rectal cancer and 3% of colon cancer, so it can be useful to test all CRC patients for HER2 gene alterations.

What is tumor testing?

Tumor testing requires a biopsy — a small tissue sample of your tumor. Tumor samples can be collected during a colonoscopy, taken from surgically removed tissue, or biopsied as an outpatient procedure.

What are liquid biopsies?

When cancer cells die, they shed fragments of their DNA into the bloodstream. This is called ctDNA. We can think of this as “tumor trash” in the bloodstream. A blood test to detect ctDNA is often called a liquid biopsy, or a blood biopsy. Some tests require just a blood sample, others require a tumor sample as well.

What is germline testing?

Germline testing is done with a routine blood sample. Most colorectal cancer cases are not caused by heritable genetic mutations. Because of this, germline testing is usually only recommended for some patients.

DNA

Deoxyribonucleic acid. A molecule found in every cell in the body, containing instructions for everything your cells need to do.

ctDNA

Circulating tumor DNA. Genetic material from cancerous cells found in the bloodstream.

TMB

Tumor mutational burden (TMB) is a measure of gene mutations found in the tumor DNA. It is expressed as number/megabase (Mb). In general, MSI-H tumors have a higher TMB (greater than 20/Mb), while MSS CRC has a much lower TMB on average (around 4-6/Mb).

CEA

Carcinoembryonic antigen (CEA) is a common tumor marker found in the blood. Testing for CEA levels can help determine if your cancer is growing, or if the cancer has returned. It’s usually included in regular blood tests CRC patients take during treatment and surveillance.

CA 19-9

CA 19-9 is not a commonly used biomarker for colorectal cancer patients, but it can be useful for people who have normal CEA at diagnosis. CA 19-9 is sometimes elevated with peritoneal metastases, and may be an additional biomarker for patients with BRAF mutations.

Sidedness

Sidedness is considered as a newer biomarker for CRC. Colorectal cancer that arises from the left and right sides of the large intestine have differences in their molecular makeup — which makes them more or less responsive to certain drug combinations.