Biomarkers commonly tested for in colorectal cancer
If you’ve been diagnosed with colorectal cancer, your doctor may order biomarker testing. A biomarker is a biological molecule which can be measured and is found in blood and other body fluids or tissues.
The presence and type of biomarkers found in your sample may help your doctor determine the treatment plan that is right for you.
All patients with colorectal cancer should undergo MMR or MSI biomarker testing
In healthy cells, a process called mismatch repair (MMR) fixes mutations when they occur in the cell. But when this process isn’t working right, the MMR system does not fix errors, causing those errors to build up. These repeated mistakes make the cell’s DNA unstable. This is called microsatellite instability (MSI).
High microsatellite instability, or MSI-H, is a biomarker for colorectal cancer. Another term for this is that the cells are “deficient” in mismatch repair, or dMMR.
There are 2 kinds of lab tests for this biomarker. Results that show your cancer has this biomarker are:
- MSI-H (microsatellite instability-high)
- dMMR (mismatch repair deficient)
If you are diagnosed with metastatic colon cancer, your doctor may also order tests for the following biomarkers:
- KRAS and NRAS mutations: Some colorectal cancers have mutations in the KRAS and NRAS genes, which can make them overactive and cause the cancer to grow
- BRAF mutation: The mutation called BRAF V600E causes cancer cells to grow and spread rapidly
- HER2 amplification: HER2 is a protein that regulates cell growth. Too much HER2 can cause cancer cells to grow and spread quickly. It is recommended that everyone with metastatic colorectal cancer undergo HER2 testing, unless there is a known RAS or BRAF mutation
Ask your doctor about biomarker testing, molecular testing, genomic testing, tumor gene testing, next-generation sequencing or mutation testing. All of these phrases refer to biomarkers.