The short answer
Precision oncology uses information about the specific genes and proteins in your tumor, found through biomarker or genomic testing, to help choose treatments more likely to work for you. Results can point to a targeted therapy, immunotherapy, a clinical trial matched to your tumor's profile, or confirm that standard treatment is still the right choice.
Precision oncology, also called personalized medicine, uses information about a tumor's specific genes and proteins to help guide treatment choices.
The starting point is biomarker testing, also called tumor genetic or genomic profiling, which looks for changes that reveal what's driving a particular cancer.
Results can point toward a targeted therapy aimed at a specific genetic change, or toward immunotherapy if certain markers suggest it's likely to help.
Testing can also match people to clinical trials based on their tumor's genetic profile, sometimes across different cancer types, through studies called basket trials.
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The full explanation.
Treatment guided by your tumor's specific biology
Precision oncology is also called personalized medicine. It is built on a simple idea. Two cancers of the same type and stage can still be driven by different genetic changes. Knowing those changes can help choose treatment more precisely than the diagnosis alone. Rather than treating "breast cancer" or "lung cancer" as one thing, precision oncology looks at what is happening inside a specific tumor.
Where it starts: biomarker testing
The base of precision oncology is biomarker testing. It goes by other names too: tumor genetic testing, molecular profiling, or genomic testing. A sample of the tumor is analyzed, usually from a biopsy or surgery. Sometimes a blood sample can be used instead. The lab looks for changes in genes or proteins that may be driving the cancer's growth. This is not the same as germline genetic testing. Germline testing looks at the genes you were born with, in every cell of your body, rather than changes found only in the tumor.
What results can change
A biomarker test result can open up a few different paths.
- Targeted therapy. Some gene changes, such as certain mutations in the EGFR gene, can be targeted by drugs made to act on that exact change.
- Immunotherapy decisions. Some markers, such as a high "tumor mutational burden," help predict whether immunotherapy is more likely to work. Immunotherapy is treatment that helps the immune system attack cancer.
- Clinical trial matching. Results can match people to trials built around a specific biomarker. That includes "basket trials," which enroll people based on a shared gene change rather than where the cancer started.
- Avoiding treatments unlikely to help. Sometimes results show that a therapy would not be expected to work for that tumor. That can spare a person the side effects and the cost of a treatment that was never likely to help.
What testing can't promise
A biomarker result that matches a targeted therapy makes that treatment more likely to help. It does not guarantee it. Tumors are not always uniform, so different parts of the same cancer can behave differently. Biomarkers can also change over time as a cancer evolves. That is one reason repeat testing is sometimes advised later on. And not every cancer has a known, targetable biomarker, even after thorough testing. Precision oncology improves the odds of finding an option that works. It is not a promise for every person or every cancer.
Why this matters for you
If you have not discussed biomarker or genomic testing with your oncology team, it is a fair question to raise. That is especially true for cancers where this testing is now routine. If you have already had testing, ask what the results showed. Ask whether they point to any option — targeted therapy, immunotherapy, or a clinical trial — that diagnosis and stage alone would not have shown.
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Common questions
What is precision oncology?
It's an approach to cancer treatment that uses information about the specific genes and proteins in a person's tumor to help choose the treatments most likely to work for them, rather than relying only on the type and stage of cancer. It's also called personalized or precision medicine.
How is this different from knowing what type of cancer I have?
Cancer type and stage are still central to treatment planning, but two people with the same type and stage of cancer can have very different genetic changes driving their disease. Precision oncology adds that additional layer of information — what specific changes are present in this particular tumor — which can identify treatment options that a diagnosis alone wouldn't reveal.
What kind of testing does this involve?
It usually starts with biomarker testing, sometimes called tumor genetic testing, molecular profiling, or genomic testing, done on a sample of the tumor (from a biopsy or surgery) or sometimes on a blood sample. This is different from germline genetic testing, which looks at inherited genes throughout your whole body rather than changes specific to the tumor.
What can the results actually change?
Results can point to a targeted therapy designed to act on a specific genetic change in the tumor, help predict whether immunotherapy is more or less likely to help based on certain markers, or match you to a clinical trial designed around your tumor's specific profile, including trials open to multiple cancer types with the same biomarker. Results can also, in some cases, show that a particular therapy would not be expected to work, sparing you the side effects of a treatment unlikely to help.
Does a targetable biomarker guarantee a treatment will work?
No. A matching biomarker makes a treatment more likely to help, but cancers can behave differently even with the same genetic change, and treatments can stop working over time as the cancer changes. Not every cancer has a currently targetable biomarker either. Testing improves the odds of finding an effective treatment — it doesn't guarantee one.
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Last updated: 2026-08-10Next planned review: 2027-02-03
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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