The role of biomarker testing in cancer

The term “biomarker” may be unfamiliar to people until they or someone they love has been diagnosed with cancer. In general terms, a biomarker is a trait that can be measured (or is expressed) in tissue, blood, or body fluids. Relative to cancer, biomarker testing, which may also be referred to as genetic testing, involves obtaining a sample of tumor material to identify genes, proteins or other molecules that can provide information about unique disease characteristics. Biomarkers are often discussed using acronyms.

Obtaining biomarker information can help oncologists determine the treatment options which may most effective based on the unique make-up of a tumor. Today this analysis is regularly offered to patients with solid tumors including colorectal cancer. Having knowledge around genetic mutations or molecular changes can often mean a targeted therapy may make sense as a treatment option.  So having this data enables personalized treatment planning, a relatively new innovation. And many targeted options are associated with fewer side effects.

Biomarker information can also aid oncologists in understanding the likely course of cancer including how aggressive it may become. This can help with patient conversations around prognosis which may be important to deciding which treatment or protocol to pursue.

There are several common biomarkers relevant to colorectal cancer. The most studied include: 

• KRAS: Mutations in the KRAS gene can influence treatment decisions and the use of certain targeted therapies. There are many clinical studies looking at therapies relative to a KRAS mutation. Testing for this is commonly offered to patients diagnosed with metastatic cancer.
• NRAS: These mutations have a very similar effect on colorectal cancer cells as KRAS mutations, but are less common.
• BRAF: Mutations in the BRAF gene may be associated with a more aggressive cancer for which targeted therapy may be recommended.
• MSI-H/dMMR: Microsatellite instability-high (MSI-H) or deficient mismatch repair (dMMR) status is a key biomarker for identifying patients who may benefit from immunotherapy.
• PD-L1: Programmed death-ligand 1 (PD-L1) expression can also help identify those patients who might benefit from immunotherapy.
• EGFR: Epidermal growth factor receptor (EGFR) expression can be targeted by certain monoclonal antibodies. This is an area of high interest to clinical researchers for new treatments.
• CEA: Carcinoembryonic antigen (CEA) is one of the first biomarkers studied and associated with colorectal cancer. It can be used to monitor treatment response and detect recurrence.

If you or a loved one has been diagnosed with colorectal cancer and have not yet been offered biomarker testing, it may be a good idea to ask if it is appropriate based on the specifics of the case. Today most larger cancer centers offer such testing and it is increasingly covered by insurance plans given how results can be used to guide treatment decisions. 

Once a sample is obtained, it may take several days or weeks to get the results. Be sure to ask your provider what the expected timeline is and how results will be communicated. Sometimes this discussion will be had at a scheduled visit though the result may appear in a patient portal application ahead of an appointment. In this case, the result may be hard to understand if it is a lab report written in clinical language. In the meantime you can write down questions about what the results mean, like:

• Is there any change to my treatment plan?
• Are there targeted therapies available?
• Does the result affect my prognosis?
• Are there any clinical trials available?

Biomarkers are a relatively new and important tool in cancer treatment planning. Understanding specific characteristics of a tumor allows healthcare providers and patients to have more informed treatment discussions. If you need further clarification about biomarker testing or results, reach out to your care team. 

References:

Biomarker Testing for Cancer Treatment | NCI
KRAS mutation in colon cancer: What does it mean? | Medica News Today
Colorectal Cancer Biomarkers [2023 Patient Guide] | Fight CRC