When it comes to colorectal cancer, biomarker testing is essential. While biomarker and genetic testing are often lumped together, they’re actually two different tests that provide distinct information. Genetic testing looks for inherited risks, while biomarker testing analyzes the unique features of the tumor itself. Biomarker testing provides crucial information about how the cancer behaves, helping doctors identify the best possible treatments for you. Think of it as creating a custom “fingerprint” of your cancer, guiding a tailored treatment approach.

Let’s break down what biomarker testing is, why every colorectal cancer patient should have it done, and how it drives today’s personalized treatment plans.

What is Biomarker Testing?

Biomarker testing examines molecules or genes within the tumor cells to uncover characteristics that can impact treatment. Unlike genetic testing, which tells you about inherited cancer risks, biomarker testing zeroes in on the cancer itself. This test identifies unique molecular markers that reveal how the tumor might respond to certain treatments.

Why It Matters: Biomarker testing isn’t optional. Every patient should have biomarker testing as part of their diagnostic journey. These biomarkers help doctors determine the most effective treatments and avoid therapies unlikely to work for you.

Biomarkers: Your Cancer’s “Fingerprint”

Biomarkers are like a personalized ID for your tumor, giving your healthcare team insights into how your cancer behaves and how it might respond to different treatments. Let’s break down some of the most common biomarkers in colorectal cancer in a way that’s easy to understand.

KRAS, NRAS, and BRAF Mutations: The Cell Growth Drivers

Think of KRAS, NRAS, and BRAF as signals that tell cells to grow. When these genes mutate, they can make cancer cells grow faster. Here’s why they matter:

KRAS and NRAS Mutations: If your tumor has a KRAS or NRAS mutation, certain targeted therapies (which work by blocking growth signals) won’t be effective. Knowing this helps your doctor skip these ineffective treatments and focus on what will actually work for you.
BRAF Mutation: A BRAF mutation can make the cancer more aggressive, but it also opens up new treatment options. Patients with this mutation often benefit from a combination of therapies that target BRAF specifically, which can be more effective than chemotherapy alone.

In Short: If your tumor has any of these mutations, doctors can use that information to guide you toward treatments that are more likely to work and away from those that won’t.

MSI-H and dMMR: Making Cancer More “Visible” to the Immune System

Microsatellite Instability-High (MSI-H) and Mismatch Repair Deficiency (dMMR) are markers that indicate the tumor has a lot of genetic “mistakes.” This can be a good thing for treatment because it makes the tumor more visible to the immune system, which can then attack the cancer more effectively.

Immunotherapy: If your tumor has MSI-H or dMMR, it’s often very responsive to immunotherapy. This treatment essentially “boosts” your immune system, helping it to recognize and fight the cancer.

In Short: MSI-H and dMMR make your tumor a prime candidate for immunotherapy, which can be a powerful treatment option.

HER2 Amplification: The Growth Accelerator

HER2 is a protein that can make cancer cells grow faster. While HER2 is more commonly associated with breast cancer, some colorectal cancers are also HER2-positive. If your tumor has a high level of HER2, it’s an indicator that the cancer may be more aggressive, but it also opens up additional treatment options.

HER2-Targeted Therapy: Treatments designed to block HER2 have been highly effective in other cancers and are now available for HER2-positive colorectal cancer. If your cancer tests positive for HER2, these therapies could play a major role in your treatment plan.

In Short: HER2-positive tumors have a “growth accelerator” that can be targeted with specific treatments, giving doctors more options for treating aggressive cancers.

What These Biomarkers Mean for Your Treatment

Biomarker testing isn’t just an added extra—it’s a key part of building your personalized treatment plan. Knowing your tumor’s biomarkers allows your healthcare team to:

Choose Treatments That Work Best for You: Biomarker testing identifies which treatments are most likely to be effective, helping avoid a trial-and-error approach.
Access Targeted and Breakthrough Therapies: Specific biomarkers connect you with cutting-edge treatments, like immunotherapy for MSI-H/dMMR tumors or HER2-targeted therapies.
Avoid Ineffective Treatments: Testing also reveals which treatments won’t work for you, saving you time, side effects, and unnecessary procedures.