Diagnosis basics · 5 min read
Biomarker testing for cancer
Biomarker testing looks for genes, proteins, or other substances that can give information about a cancer and possible treatment options.
Written by OncosAI Editorial Team · Editorial review 2026-07-04
Key takeaways
- Biomarker testing can help match some patients to targeted therapy or immunotherapy.
- Not every cancer needs the same tests.
- A negative result does not mean there are no treatment options.
- Ask whether testing was done on tissue, blood, or both.
What biomarkers are
A biomarker is a measurable sign in tissue, blood, or another body fluid. In cancer care, biomarkers may help identify what is driving a tumor or how it may respond to treatment.
Examples include gene mutations, rearrangements, protein expression, receptor status, or immune-related markers.
How testing can affect treatment
Some cancer medicines are approved for tumors with specific biomarkers. Testing can also help doctors decide whether certain treatments are unlikely to help or whether a clinical trial may be relevant.
Questions to ask
- Which biomarker tests are standard for my cancer type?
- Were the results complete or is more tissue needed?
- Could a blood-based test add useful information?
- Do any results point to targeted therapy, immunotherapy, or trials?
- Should testing be repeated if the cancer changes?
Sources
- National Cancer Institute: Biomarker Testing for Cancer Treatment — Explains biomarker testing and how it may guide treatment.
- American Cancer Society: Biomarker and Tumor Marker Tests — Patient guide to biomarker tests and when they may be used.
This guide is educational and does not replace advice from your oncology care team.