Biomarker Resource Center
Colon Cancer Biomarkers
Reviewed by XpertPatient Medical Advisory · Updated June 2026 · Sources: NCI · ACS · ASCO · NIH/PMC
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What is a biomarker?
A biomarker is a signal your cancer leaves behind. Doctors find these signals in your blood or tumor tissue. The signals tell your doctor important things — like what type of cancer you have and how it is behaving.
Think of it like a clue. Your doctor collects clues from your biomarker test results. Those clues help build a picture of your cancer. That picture helps your doctor and you have a more informed conversation about next steps.
Everyone’s cancer is different — even people with the same type of cancer can have very different results. That is why biomarker testing matters. It helps your care team understand your cancer specifically.
For Colon Cancer
Why do biomarkers matter in colon cancer?
In colon cancer, biomarker testing is commonly done before care decisions are made. The results give your doctor important information about your specific tumor. Some results tell your doctor which approaches are commonly used — and some tell your doctor which ones are not likely to help. This protects you from approaches that may not be right for your cancer.
💬 A good question to ask your doctor: Ask your doctor whether RAS and MSI testing have been done on your tumor. These are commonly recommended before care decisions are made in colon cancer.
The most important colon cancer biomarkers are RAS mutation status and MSI testing. Together they tell your doctor which treatment approaches are likely to help and which are not, before care decisions are made.
Patient Poll
Have you had biomarker testing for your colon cancer?
The Tests Your Doctor May Order
🔍 Does your tumor have a mutation that affects which approaches may help?
RAS mutations are found in about half of all colon cancers. This result gives your doctor important information about which approaches are likely to be useful and which are not. Ask your doctor what your RAS result means for your care and how it fits into the overall picture.
🔍 How does your tumor’s DNA repair system work?
MSI-H means your tumor has a change in how it repairs DNA. This is a finding that your doctor will use as part of the conversation about your care. Ask your doctor whether MSI testing has been done and what your result means for your situation.
🔍 Is there a specific mutation in your tumor?
BRAF V600E is a mutation found in some colon cancers. Knowing whether your tumor has this mutation gives your doctor useful information. Ask your doctor whether BRAF testing was done and what the result means for your care.
Watch & Learn
Important: This page is for education only. It is not medical advice. Every patient’s situation is different. Please talk to your doctor or care team about what your biomarker results mean for you specifically.
Common Questions
Colon Cancer Biomarkers — Your Questions Answered
Should I ask about RAS and MSI testing?
Yes. These tests are commonly recommended before care decisions are made in colon cancer. If you are not sure whether they have been done, ask your doctor or care team.
What does MSI-H mean for my care?
MSI-H is a finding that your doctor will consider when talking with you about your care. Ask your doctor what your MSI result means for your specific situation and what approaches are commonly used for this finding.
Can I ask for genetic testing if my doctor has not ordered it?
Absolutely. You can always ask your doctor whether additional testing makes sense for your situation. It is a reasonable question and your care team can help you decide together.
Should I ask about clinical trials?
Clinical trials can be an important option for some patients. Ask your doctor or visit clinicaltrials.gov to learn whether any trials may be relevant for your situation.
Quick Links
From the Colon Cancer Center on XpertPatient
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