by Ella Strickler and medically reviewed by C.H. Weaver, MD
- Overview
- Testing for biomarkers
- Biomarker identification techniques
- Interpreting your biomarker report
- Biomarkers commonly found across tumor types
What are biomarkers?
Biomarkers are like biological fingerprints, and each tumor has its own unique set. These markers can provide important clues about how to detect, understand, and treat cancer.
A biomarker is usually DNA, RNA, or protein found in blood, tissues, or other bodily fluids. There are several types of cancer biomarkers, each serving a different purpose.
- Diagnostic biomarkers can help detect or confirm the presence of cancer.
- Prognostic biomarkers can indicate the likely outcome of a disease regardless of treatment.
- Predictive biomarkers indicate the likelihood that an individual will benefit from a specific therapy.
Because biomarkers provide personalized information about a specific cancer, they can help guide more effective care. If you have been diagnosed with advanced and recurrent cancer and haven’t had biomarker testing, ask your doctor whether testing is recommended for your tumor type. In many cases, biomarker testing can help identify treatments or clinical trials that are more likely to work for you.
How do physicians test for biomarkers?
The physical testing process for biomarkers involves collection of a sample, such as from of blood or tissue. The sample is then analyzed in a laboratory using biomarker identification techniques to look for specific genes, proteins, or other molecules.
What common biomarker identification techniques exist?
- FISH (Fluorescence in Situ Hybridization) uses DNA/RNA probes with fluorescent tags to look for altered genes in a sample
- IHC (immunohistochemistry uses protein-specific tags (dyes) to identify certain proteins in a tissue sample.
- NGS (next-gen sequencing) reads all the DNA or RNA in a sample at once to find biomarkers
- PCR (polymerase chain reaction) takes a tiny piece of DNA or RNA from a sample and makes many copies of it to help find specific biomarkers.
- RNA-seq (RNA sequencing) detects biomarkers by measuring whether RNA levels in a sample are higher or lower than expected.
Interpreting your biomarker report
Biomarkers are often both cancer-specific and person-specific, meaning that they can vary between different types of cancer and from one patient to another with the same disease. While it is possible for a single patient to have multiple biomarkers, not all of them are clinically relevant. Some may have no known role in disease progression or response to therapy. In many cases, only a subset is considered actionable for guiding targeted treatment.
Actionable findings are test results that provide clear guidance for treatment or decision-making based on established medical evidence. These findings and their implications can differ depending on whether they arise from germline or somatic (tumor) testing.
Germline testing involves analyzing germline DNA, found in reproductive cells (eggs and sperm). Alterations to this DNA can be passed down from parent to child. Some people inherit germline mutations that increase their risk of developing cancer, so germline testing can guide efforts to prevent, monitor, or treat inherited biomarkers of cancer.
Possible actionable findings include:
- Pathogenic finding: a genetic alteration that is known to cause disease
- Variant of unknown significance: a genetic alteration that may or may not cause disease
- Benign variant: a genetic alteration that is known not to cause disease
Somatic testing looks at changes (alterations) in DNA that occur in non-reproductive cells. Unlike germline alterations, somatic alterations develop over a person’s lifetime and are not passed from parent to child. Most cancers are caused by somatic mutations, so somatic testing can help identify the specific changes driving a tumor’s growth.
Actionable findings from somatic testing include:
- Whether you qualify for an FDA-approved therapy for your disease
- Whether you qualify for a clinical trial
- Whether you qualify for an existing FDA-approved therapy for a different tumor type
It is important to consult with your physician and genetic counselor to ensure that you have an accurate understanding of your results and their implications.
Biomarkers commonly found across tumor types
While some cancer biomarkers are specific to only one or two types of cancer, others are reported across many different cancer types. These biomarkers may be treated with targeted or immunotherapies or indicate eligibility for a clinical trial. Common biomarkers of this nature include:
| Biomarker | Tumor types | Actionability (Based on current NCCN guidelines)1 | Implications or available targeted/ immunotherapy |
| ALK | Non-small cell lung cancer (NSCLC), anaplastic large cell lymphoma, neuroblastoma, others | Category 1 (strong evidence to support actionability; strong expert agreement) | ALK inhibitors |
| BRAF V600E | NSCLC, melanoma, thyroid, gastric | Category 1 (NSCLC) | BRAF and/or MEK inhibitors |
| BRCA1/2 mutations | Breast, ovarian, prostate, pancreatic | Category 1 (breast/ovarian); 2A others | PARP inhibitors |
| EGFR mutations | NSCLC | Category 1 | EGFR inhibitors |
| HER2 (ERBB2) | Breast, colorectal, gastric, NSCLC | Category 1 (breast); 2A (gastric); 2B (NSCLC) | HER2-targeted therapy |
| KRAS/NRAS mutations | Colorectal, NSCLC, pancreatic | Category 2A (lower evidence, general agreement among experts) | KRAS G12C targetable |
| MET exon 14 skipping | NSCLC | Category 1 | MET inhibitors |
| MSI/MMR (microsatellite instability/mismatch repair) | Colorectal, gastric, endometrial, others | Category 1 | May be targeted with immunotherapy |
| NTRK fusions | Many cancers | Category 2A | TRK inhibitors |
| PD-L1 (programmed cell death ligand 1) | Gastric, NSCLC, melanoma, others | Category 1 (strong evidence to support actionability; strong expert agreement) | May be targeted with immunotherapy |
| PIK3CA | Breast | Category 1 | PI3K inhibitors |
| RET fusions | NSCLC, thyroid, others | Category 1 | RET inhibitors |
| TMB- H (high tumor mutational burden) | Many types of solid tumors | Category 2B (less evidence to support actionability; some expert agreement) | May be targeted with immunotherapy |
Reference:
- Biomarkers Compendium. (2025). National Comprehensive Cancer Network. Retrieved July 13, 2025, from https://www.nccn.org/compendia-templates/compendia/biomarkers-compendium
