An Introduction to Colorectal Cancer Biomarkers

There’s more to a cancer diagnosis than a death sentence. Every patient’s and survivor’s journey is unique, and with early detection and appropriate treatment, the chances of survival and complete recovery are high, especially for colorectal cancer.

An important part of detection, diagnosis and treatment is your cancer biomarker profile, but what is a biomarker exactly?

Biomarkers are indicators of abnormal processes, conditions, or diseases present in the body. These can be found in the blood, other bodily fluids or tissue. Biomarkers can be categorized into molecular, histologic, radiographic, or physiologic biomarkers.

Molecular biomarkers are, simply put, measurable molecules found in biological samples. For example, fecal occult stool tests use the presence of blood as biomarkers for potential colorectal cancer diagnosis.

Radiographic biomarkers are obtained from imaging studies, such as the presence of metastatic colorectal cancer spread to the liver and lungs through a computed tomography (CT) scan.

Histologic biomarkers come from examining any biochemical alterations in the cells or tissue, such as examining the tumor or polyp tissue to determine the colorectal cancer stage.

Physiologic biomarkers are related to the functional processes of the body, such as blood flow and pressure.

Types of cancer biomarkers

Biomarkers have many applications and different biomarkers tell different stories about your body. Some are useful in identifying the type of cancer you have, while others help determine if the available treatments will be effective.

Diagnostic biomarkers help identify the type of cancer.

Prognostic biomarkers are useful in estimating the course of the cancer if it is left untreated.

Predictive biomarkers, as the name suggests, predicts whether or not the body will respond to a specific treatment.

Pharmacodynamic biomarkers are useful in determining the appropriate treatment dose.

Recurrence biomarkers are used to monitor if a cancer has returned after treatment.

As with other cancers, biomarker tests for colorectal cancer are typically conducted on the tissue sample collected through biopsies. As cancer treatments are expensive and have different side effects, determining the most appropriate treatment is particularly important for both effective treatment and the patient’s well-being.

Biomarker tests to help select the right treatment usually look for genetic markers, such as mutations in genes known to be related to colorectal cancer, including the BRAF, KRAS and NRAS genes. This is not always the case, as biomarker tests may also look for proteins and other molecules, such as carcinoembryonic antigen (CEA), a molecule made of protein and carbohydrate chains that are expressed in colorectal tumor cells.

Biomarker tests for genes and proteins can sometimes be conducted singularly, while other tests that can check for multiple markers are known as multigene or panel tests.

Genetic biomarker tests may examine only the genes in your cancerous cells — a process known as whole-exome sequencing — or look at all of the DNA, including non-genes, in a test known as whole-genome sequencing. These tests are also able to look at the number of genetic changes in what’s referred to as tumor-mutational burden.

While these tests may identify abnormalities in your genetic material, further analysis is still required to determine which treatments will be most effective for your cancer.

Your doctor may order biomarker tests before or during treatment, usually after your diagnosis and before you select your treatment plan. Tests may be conducted again after treatment to determine if all the cancer has been removed and again after a period of recovery to check for any cancer relapse.