The Influence of Biomarker Testing in the Treatment of Colorectal Cancer

Recent clinical advancements have shed additional light on the relationship between changes in DNA and cancer — specifically, how those changes influence the way colorectal cancer and other cancers may respond to treatment. Traditionally, the type of cancer, the stage, and the patient's overall health were the primary factors that determined a recommended treatment plan. However, oncologists can now use biomarker testing for some patients to understand better how best to treat the patient.

Biomarkers: What Are They and How Are They Identified?

A biomarker, short for biological marker, is a specific molecule found in cancer cells, surrounding tissue, and bodily fluids like blood. Biomarkers, sometimes called molecular markers, provide important information about the characteristics of the cancer.

Biomarker testing (also called genomic testing or molecular testing) takes place after a colorectal cancer diagnosis. Testing often involves a blood draw or removing some tissue from the tumor during a biopsy or surgery. Collected samples are sent to a lab and analyzed by a pathologist. Knowing if biomarkers, such as abnormal proteins or genetic mutations, are present gives the cancer care team more insight into what types of treatment will work.

Several different biomarkers are specifically related to colorectal cancer, including BRAF, DPYD, KRAS, NRAS, MSS, EFGR, HER2, NTRK, CEA, PTCH1, TRK fusions, TMB, Sidedness, UGT1A1, and MSI-H/dMMR. Some colorectal cancer patients will have a genetic mutation present, while others will not. The cancer specialists will specifically design a treatment plan based on the findings.

It’s important to understand that biomarker testing isn’t looking for inherited genetic mutations but rather acquired mutations, which develop at some point during a person’s lifetime. Still, you should talk with your doctor about any known family history that involves precancerous polyps.

Which Colorectal Cancer Patients Should Undergo Biomarker Testing?

After receiving a colorectal cancer diagnosis, your cancer care team may recommend biomarker testing to determine if any mutations are present in your DNA. The earlier you are tested, the sooner the oncology team can develop the most beneficial treatment plan based on the results and other factors.

• Patients diagnosed with metastatic (stage IV) colorectal cancer may get tested for at least four predictive biomarkers: BRAF, KRAS, NRAS, and HER2
  

• Testing for other biomarkers, such as carcinoembryonic antigen (CEA), may take place during follow-up visits for patients diagnosed with stage II, III, or IV colorectal cancer. This testing helps determine if the cancer has recurred or to gain additional information about the tumor that could impact treatment.

• Regardless of the stage, any patient may be tested for an abnormality known as MSI-H (“microsatellite instability-high"), which indicates a Lynch syndrome gene mutation. MSI-H is also known as mismatch repair deficiency (dMMR or MMR-D).

Understanding what biomarkers exist, if any, can help determine which treatments will best target colon or rectal cancer. If you have already had surgery and aren’t sure if the tumor was tested for biomarkers, ask your doctor.

Common Biomarker Tests for Colorectal Cancer

Various types of biomarker tests can be used for colorectal cancer. Some tests check for a single biomarker, while others check for multiple biomarkers at the same time. The two most common types of biomarker testing are genetic biomarker tests and protein biomarker tests.

Genetic Biomarker Tests

Several different genes are evaluated in the testing process. As more clinical research is conducted, new genes are added to the list. The oncologist may adjust the course of treatment in cases where a mutation is detected.

Protein Biomarker Tests

Some biomarker tests look for proteins rather than genetic markers. One example is CEA, a protein that becomes elevated when the colon is inflamed. Higher levels of this protein are often found in colorectal cancer patients.

Additional Biomarker Tests for Colorectal Cancer

Your colorectal cancer doctor may want to evaluate other biomarkers, such as sidedness and pathways, in addition to genetic and protein biomarkers.

• Sidedness refers to the side of the colon that is affected by cancer. Right-sided tumors and left-sided tumors don’t necessarily share the same characteristics, therefore causing them to respond to treatment differently.

• Pathways or signaling pathways are biomarker types that evaluate the behavior of cancer cells. Common biomarker pathways that may be tested in colorectal cancer patients include the PD-L1 pathway, tumor mutational burden (TMB), and WNT pathway.

How Biomarker Testing Results Help Oncologists Create a Personalized Treatment Plan

Colorectal cancer treatment options continue to expand as clinical research reveals new information. With more knowledge regarding the importance of biomarker testing, oncologists can develop treatment plans that are as unique as the patient. Treating cancers, such as colorectal cancer, based on your genes or any mutations is called “precision medicine” or “personalized medicine.”

Patients with a biomarker present may benefit from a specific targeted therapy drug that can effectively slow the growth of or kill their cancer cells. Many types of targeted therapies are available, each designed to work with such precision that cancer cells can be identified while leaving healthy cells alone.

As with all types of cancer treatment, what’s suitable for one patient may not be best for another. While a specific targeted therapy may work best in a patient with a known biomarker, a patient with no biomarker(s) present may likely respond well to a different type of colorectal cancer treatment. Your colorectal cancer care team will review biomarker testing results to determine what will work best in your situation.

What to Do After a Colorectal Cancer Diagnosis

If you’re newly diagnosed with colorectal cancer or have colorectal cancer that has returned, biomarker testing can allow for a more effective treatment. Based on your biomarker test results, you can receive a plan that is personally tailored to your specific needs, using the most advanced colon and rectal cancer treatments available.

Our dedicated team of specialists is here to help care for you every step of the way. We are located throughout the south Chicago suburbs, making it easy for you to receive quality cancer care close to home. Request a consultation to talk about available treatment options or to request a second opinion regarding a diagnosis or treatment recommendation you’ve already received.

Categories: Colorectal Cancer