The right set of treatments for each patient diagnosed with cancer is determined by many different factors. For decades it has primarily been the type of cancer, hormone status (in some cases), the stage, and the patient’s overall health. However, in recent years, it’s become possible to evaluate genetic changes in the patient’s DNA to direct the treatment plan. This is called biomarker testing. It’s sometimes also referred to as genomic testing or molecular testing.
How do the results of biomarker testing impact the way patients are treated for colorectal cancer?
What is Biomarker Testing for Colorectal Cancer?
A biomarker test looks at a sample of the patient’s tumor tissue sample to identify whether there are abnormal proteins or genetic mutations present. This data gives the cancer care team more direction as to which treatments are likely to work best, which ones will not work, and what might happen in the future. It’s important to note that most of the genetic mutations are not hereditary. Read more about whether colon cancer is heredity in our blog.
The genetic changes being monitored in these tests are not inherited genetic mutations, but rather changes in your own genetic makeup that have developed over time. They can sometimes be related to a specific cause such as the chemicals in tobacco smoke. And other times, there’s no clear reason as to why the gene has mutated.
Not every patient with colorectal cancer will have a genetic mutation present. If none are found, it directs the cancer specialists on which treatments to use, and which are not likely to work.
Who is Tested and What Are They Looking For?
At this time, patients with metastatic (stage IV) colorectal cancer are the primary group eligible for biomarker testing to determine which targeted therapies, if any, would work best. Ideally, the testing is done before a treatment plan is created. The tissue of the tumor can be tested if it’s removed through surgery or a biopsy.
If you had surgery already, ask your oncologist if they tested the tumor for biomarkers. And if not, can it be done now? There may be information available that would alter the direction of your treatment plan.
Types of Biomarker Tests for Colorectal Cancer
There are quite a few types of biomarker tests that can be used for colorectal cancer including: diagnosis, understanding if the cancer is recurring, and to see how well a treatment plan is working. Here we’ll focus on two types of biomarker testing that are most common.
Genetic Biomarker Tests
There are quite a few different genes that are evaluated in the testing process. The list continues to grow as more clinical research is conducted. If a mutation is present in one of these, the course of treatment may be adjusted.
Common genetic biomarkers used in colorectal cancer include:
- BRAF is a gene that triggers cell division. This test is commonly recommended for stage IV cancer patients.
- KRAS is a gene that controls the production of the K-Ras protein. This protein tells the cells when it’s time to grow, mature, or take on various functions. If mutated, the on-off switch doesn’t work and cells grow uncontrollably.
- NTRK Fusions is a genetic abnormality that happens when two genes become fused, causing signaling to be thrown off and leading to cancerous cell growth.
- HER2 is a gene that controls the growth of the HER2 protein. Too many HER2 receptors will cause the cells to grow too rapidly.
There are additional genes that can be tested for mutations. These are some of the most common ones for colorectal cancer.
Protein Biomarker Tests
Other biomarker tests look for proteins rather than genetic markers. One example of protein biomarkers used in colorectal cancer is CEA. This is a protein that is typically elevated in patients with colorectal cancer. This protein becomes elevated when the colon is inflamed.
Other Types of Biomarker Tests for Colorectal Cancer
Genetic biomarker tests and protein biomarker tests are only two types of biomarkers that are looked at in patients who have colorectal cancer. Your doctor may also want to evaluate other biomarkers, such as sidedness and pathways.
Sidedness is the side of the colon that is affected by cancer. Sometimes, right-sided tumors might respond better to certain treatments when compared with left-sided tumors.
Pathways or signaling pathways are a type of biomarker that evaluates the behavior of the cancer cells. Some common biomarker pathways that you may be tested for if you have colorectal cancer include the PD-L1 pathway, tumor mutational burden (TMB), and WNT pathway.
Tumor Pathways
There may also be a discussion about pathways. This type of biomarker determines the behavior of cancer cells. The PD-1/PD-L1 and Wnt pathways are commonly discussed in colorectal cancer research and are targets for some treatments.
How Do Oncologists Create a Personalized Treatment Plan Using Biomarker Testing?
As clinical research progresses, colorectal cancer treatment options have expanded. Today, oncologists are able to create treatment plans that are highly specific to the patient’s needs. The biomarker testing results guide the treatment planning process. If a biomarker is present, there may be a specific targeted therapy drug available to slow the growth of the cancer cells. Some of the most common gene mutations or pathways that can be treated include:
- BRAF is a genetic biomarker that can be mutated in patients with colorectal cancer. There are specific drugs called BRAF inhibitors that are used in patients who have this type of mutation. Some studies have found that BRAF inhibitors can lower the risk of death in patients who have colorectal cancer.
- RAS genes including KRAS, HRAS and NRAS are tested for mutations. When mutations exist in these genes, abnormal proteins can result in constant uncontrolled cell division. There are specific chemotherapy drugs designed for patients with this type of mutation, such as FOLFOX, CAPOX, and FOLFIRI.
- HER2-positive colorectal cancers indicate there is too much HER2 protein being created with too many receptors on the cells causing them to grow uncontrollably. Blocking the receptors from receiving too much HER2 protein can slow the growth of cancer cells.
- NTRK fusions present in patients with metastatic colorectal cancer that isn’t responding to standard therapies can be treated with FDA approved NTRK inhibitors.
As with all types of cancer treatment, what’s right for one patient may not be best for another. Your colorectal cancer care team will review biomarker testing results to determine the best path forward.
What to Do if You’ve Been Diagnosed With Colorectal Cancer
If you recently received a diagnosis of colorectal cancer or you have recurring colorectal cancer, it’s a good idea to meet with a medical oncologist before having surgery. The surgeon and the oncologist can then work together to create a plan that would work best for you, including the decision to run biomarker testing.
Learn more about who is on your colorectal cancer care team.
Rocky Mountain Cancer Centers provides personalized treatment for patients with all stages of colorectal cancer at our locations throughout the Denver area, Colorado Springs, and the front range. Request a consultation – whether it’s your first or a second opinion – to talk about the treatment options available to you.
