Lung Cancer Biomarker Testing: What to Ask Before Treatment Starts

You’ve just been told you have lung cancer, and you want treatment to start now. Then the oncologist says something that sounds strange: let’s wait for the biomarker results.

That wait has a purpose. Lung cancer biomarker testing looks for specific changes inside your tumor, and in India those changes turn up often. Around 3 in 10 people with non-small cell lung cancer (NSCLC) have an EGFR or ALK change that a targeted medicine can act on. Among people with adenocarcinoma, a pooled analysis of Indian studies puts it closer to 4 in 10. For many of them, the first treatment ends up being a tablet taken at home, with chemotherapy kept for later.

Below is what the test looks for, who needs it, and the questions worth asking before anyone writes a prescription.

What a Biomarker Actually Is

A biomarker is something in your tumor that tells your doctor which treatment is likely to work. In lung cancer it’s usually a change in a gene: a mutation, or a fusion, where two genes break and join together. Sometimes it’s a protein sitting on the surface of the cancer cells.

Why does this matter? Two people with the same type and stage of lung cancer can have tumors driven by completely different changes. One tumor runs on an overactive EGFR gene and shrinks with an EGFR-blocking tablet. Another runs on an ALK fusion, and that same tablet would do very little.

The test is usually done on the tissue taken during your biopsy. Sometimes a blood sample is used instead.

Will This Tell Me If My Children Are at Risk?

Almost never. These changes happened in the tumor during your lifetime. You weren’t born with them, and you can’t pass them on. If your doctor thinks an inherited risk is possible, that’s checked with a separate test.

Who Needs Testing

If you have advanced non-small cell lung cancer of the non-squamous type, which mostly means adenocarcinoma, you should be tested. That’s the standard set by the National Comprehensive Cancer Network (NCCN), and most cancer centers follow it.

Testing is also worth discussing if:

• you have squamous cell lung cancer and you’ve never smoked, or smoked very little
• your cancer was caught early and removed with surgery, since some results now shape the treatment that follows the operation

Small cell lung cancer is a separate disease. It’s treated another way, and these tests don’t steer its treatment.

“But I Smoked for 30 Years”

People sometimes assume testing is only for non-smokers. EGFR and ALK changes do show up more often in people who never smoked. Smokers have them too, though, and one biomarker, KRAS G12C, is more common in smokers. Your smoking history shouldn’t decide whether you’re tested.

The Biomarkers on Your Report

There are now more than ten biomarkers on the guideline list for advanced NSCLC. In January 2025, NCCN added seven more, NRG1 and FGFR among them. You don’t need to memorize them. Knowing the main names helps you recognize them on your report.

EGFR, ALK and ROS1 are the ones you’ll hear about most, and each has its own targeted tablets. When EGFR comes back positive, an EGFR-targeted tablet is often the very first treatment.

BRAF V600E, MET exon 14 skipping, RET and NTRK changes are less common, but each also has a matched targeted medicine. For BRAF, that’s usually a combination of two drugs. NTRK inhibitors are unusual because they work across many different cancer types.

KRAS G12C and HER2 changes have targeted options too, though these are mainly used after a first treatment has been tried. NRG1 is one of the newest targets on the list, and treatments for it are still developing.

PD-L1 is the odd one out. It’s covered further down.

The India numbers are worth knowing. In one study of more than 3,000 Indian patients, 29% had an EGFR change, 8.1% had ALK and 3.5% had ROS1. That EGFR figure is more than double the roughly 13% seen in Caucasian patients, and close to what’s reported in East Asia. So an EGFR-positive report is one of the most common results an Indian patient can get.

Where PD-L1 Fits In

PD-L1 is measured differently from the rest. It’s a protein, checked with a lab stain called immunohistochemistry (IHC). A high PD-L1 level suggests immunotherapy may work well. It can’t tell you anything about EGFR, ALK or the other genes, so you’ll usually need both results.

How the Testing Is Done

From Biopsy to Gene Panel

Most labs test the tissue from your biopsy using next-generation sequencing, or NGS. One NGS run checks dozens of genes at the same time. The older approach, testing one gene after another, has a real drawback. Lung biopsy samples are often small, and the tissue can run out before every gene has been checked.

Some labs add an RNA-based test, which picks up certain fusions (ROS1, RET, NTRK) more reliably than DNA testing alone.

The Blood Test Option

A liquid biopsy looks for small pieces of tumor DNA in your blood. It’s useful when the tissue sample was too small, or when another biopsy would be risky. If it finds a change, your doctor can act on that result. If it finds nothing, the picture is less clear. The tumor may still carry a change the blood test missed, so your doctor may want tissue tested as well.

Ask Which Genes Are Covered

Panels vary in size. A 2026 review of targeted NGS panels found that only 6% covered all 12 biomarkers NCCN recommended at the time. So it’s a fair question to ask: which genes does my test look at?

Waiting for Results

There’s a good reason not to rush, and it has to do with immunotherapy. NCCN guidelines say molecular results should be in hand before starting checkpoint inhibitors, a common type of immunotherapy. If your tumor turns out to be EGFR- or ALK-positive, a targeted tablet is usually the better first choice.

Some people are too unwell to wait. In that case, your oncologist may start treatment right away and change course once the results arrive. Ask what the plan is for your situation.

When the Results Come Back

If the report shows a driver change, your treatment will most likely be a targeted medicine matched to it. Many of these are tablets taken once or twice a day at home. You’ll still have regular scans and blood tests to check that it’s working.

If no driver change turns up, the usual options are immunotherapy, chemotherapy, or the two together. Your PD-L1 result helps your oncologist choose.

Each biomarker comes with its own treatment choices and its own pattern of resistance. For a closer look at how biomarker results guide lung cancer treatment, this explainer goes through them one by one.

If the Cancer Grows Again

Targeted treatment can keep lung cancer under control for a long time. Tumors adapt, though. When the cancer starts growing again, another biopsy, from tissue or blood, can show what changed. With EGFR-positive cancer, for example, the tumor may pick up a second EGFR mutation or start relying on MET amplification. That new result points to the next treatment.

Questions to Bring to Your Appointment

Write these down, or take a screenshot:

1. Was my tumor tested for all the recommended biomarkers, or only EGFR?
2. Was it a full NGS panel? Which genes were included?
3. Has PD-L1 been checked?
4. If there wasn’t enough tissue, could a blood test fill the gap?
5. When will the results be ready, and what happens until then?
6. If this treatment stops working, will the tumor be tested again?
7. Does my insurance or a government scheme cover the test? 

Before Treatment Starts

Lung cancer biomarker testing is what makes a precise treatment plan possible. In India, where EGFR and ALK changes are common, it decides the first treatment for a large share of patients. Make sure your tumor has been fully tested, ask what each result means, and keep a copy of the report. You’ll probably need it again if your treatment changes.

Common Questions

Do I need biomarker testing for small cell lung cancer?

Generally not in the same way. Small cell lung cancer is treated differently, and these tests don’t currently steer treatment choices for it. Your oncologist can tell you if anything applies in your case.

Can it be done with a blood test?

Yes, through a liquid biopsy. It’s useful when tissue is limited. A negative blood result may need to be double-checked with a tissue sample.

My results were negative. Does that mean fewer options?

It means a targeted tablet probably isn’t the first step. Immunotherapy, chemotherapy, or both are standard choices for people without a driver change, and they can work well. Your PD-L1 result helps guide which one.