What is PD-L1 testing for lung cancer?

Think of PD-L1 as a “cloaking device” used by some cancer cells. It is a protein that sits on the surface of cells and sends a “do not shoot” signal to your immune system. When cancer cells have a lot of PD-L1, they can effectively hide from your body’s natural defenses.

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PD-L1 Testing: How Your Score Shapes Your Lung Cancer Treatment

Dr. Julie Brahmer of Johns Hopkins joins patient host Colette Smith to demystify PD-L1 testing, explain what your Tumor Proportion Score (TPS) really means, and reveal the questions every lung cancer patient should be asking their oncologist about immunotherapy.

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The Tumor Proportion Score (TPS) Explained

When your doctor tests your tumor for PD-L1, the results are usually given as a Tumor Proportion Score (TPS). This is simply the percentage of cancer cells in your sample that “test positive” for the PD-L1 protein.

High (50% or greater)

The cancer is using the PD-L1 “cloak” heavily. These tumors often respond very well to immunotherapy alone.

Low (1% to 49%)

Some PD-L1 is present. Doctors may recommend a combination of immunotherapy and chemotherapy.

Negative (Less than 1%)

There is little to no PD-L1 visible. This doesn’t mean immunotherapy won’t work, but your doctor will likely look closer at other biomarkers or combination treatments.

Why This Matters for Your Treatment

Knowing your PD-L1 score helps your care team decide if immunotherapy is the right “key” to unlock your immune system’s ability to find and fight the cancer. It is one piece of the puzzle, often used alongside NGS (Next-Generation Sequencing) to create a personalized treatment plan.

NOTE: Your PD-L1 status is not a “grade” or a “stage.” It is a roadmap that helps your doctors choose the most effective medicine for your specific type of lung cancer.

Frequently Asked Questions about PD-L1 Testing for Lung Cancer

No. A PD-L1 score is not a measure of how aggressive your cancer is or what stage it is. Instead, it is a “biomarker” that helps your doctors understand how the cancer behaves and which treatments (like immunotherapy) are most likely to work.

Yes, it’s possible. Biomarker levels can sometimes shift after certain treatments or as the cancer evolves. This is why doctors may sometimes request a new biopsy if the cancer returns or progresses.

A “negative” result doesn’t mean immunotherapy won’t work at all, but it may mean it isn’t the best first option. Your doctor will look at your NGS (Next-Generation Sequencing) results to see if a targeted therapy is a better fit.

Typically, PD-L1 results come back faster than broader genomic testing—usually within 2 to 7 days. Most care teams wait for both the PD-L1 and NGS results before finalizing a treatment plan.

Not exactly. PD-L1 is a protein test (looking at the surface of the cell), while genomic testing (like NGS) looks at the DNA inside the cell for mutations like EGFR or ALK. You need both to have a complete picture.

Resources & Downloadable Guide

thumbnail image of the downloadable pdf Questions to ask your doctor about PD-L1

Prepare for Your Next Appointment

Navigating a lung cancer diagnosis is overwhelming, and remembering every detail during a brief medical appointment is difficult. We’ve created a simple, one-page guide to help you advocate for the best possible care.

Get our printable PDF, Questions to Ask Your Care Team about PD-L1

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