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PDL1 (Immunotherapy) Tests
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

PDL1 (Immunotherapy) Tests

A PD-L1 test measures the amount of the PD-L1 protein on cancer cells to determine if a patient is a candidate for immunotherapy treatment.

What is a PD-L1 test?

PD-L1 (programmed-death ligand 1) is a protein normally found on healthy cells that acts as a "brake" on the immune system, preventing it from attacking healthy tissue. Some cancers use this protein to hide from the immune system. If a tumor has high levels of PD-L1, providers may use immune checkpoint inhibitors—a type of immunotherapy—to "release the brakes" and allow the immune system to target and kill the cancer cells.

Why do I need a PD-L1 test?

Testing is used to guide treatment decisions for various cancers, including:

  • Non-small cell lung cancer
  • Melanoma
  • Hodgkin lymphoma
  • Bladder, kidney, and breast cancer
  • Head, neck, esophageal, stomach, and cervical cancers

The results help providers decide between monotherapy (immunotherapy alone) or combination therapy (immunotherapy plus chemotherapy).

What happens during the test?

The test requires a tissue sample from a tumor, obtained via:

  • Needle biopsy: Using a fine or core needle to remove cells or tissue.
  • Surgery: Removing a portion or the entire tumor.
  • Endoscopic biopsy: Using a flexible tube with a camera to collect tissue from inside the body.

What do the results mean?

Results indicate whether your tumor has enough PD-L1 to potentially benefit from specific immunotherapy medications, such as pembrolizumab, nivolumab, or atezolizumab.

  • Positive result: Your tumor cells have sufficient PD-L1, making you a candidate for immunotherapy.
  • Negative result: Your tumor cells do not have enough PD-L1, suggesting immunotherapy may not be effective, and your provider will explore other treatment options.

Scoring systems, such as Combined Positive Score (CPS) or Tumor Propositional Score (TPS), may be used to quantify the results. Because these systems vary by test type, you should discuss your specific results with your health care provider.

Frequently Asked Questions

positive result generally means the tumor expresses enough PD-L1 to qualify for specific immunotherapy drugs, but the exact threshold depends on the cancer type and the specific drug being considered. The Combined Positive Score (CPS) is a specific scoring method used primarily for cancers like gastric, esophageal, and head and neck cancers. It counts both PD-L1-positive tumor cells and PD-L1-positive immune cells (like macrophages and lymphocytes) within the tumor. A higher CPS number indicates a greater density of these cells, which can help predict a stronger response to certain checkpoint inhibitors.
Not necessarily. A negative PD-L1 result indicates that immunotherapy alone is unlikely to be effective, but it does not rule out all immunotherapy options. In many cancer types, such as non-small cell lung cancer, patients with low or negative PD-L1 levels may still benefit from combination therapy, where immunotherapy is paired with chemotherapy. Your oncologist will evaluate your overall health, cancer stage, and other biomarkers to determine if a combination approach is appropriate.
Standard PD-L1 immunohistochemistry tests typically take 5 to 10 business days to process and report. If the initial biopsy sample is too small, degraded, or does not contain enough viable tumor cells, the lab may flag the result as "non-diagnostic." In this case, your provider will likely schedule a repeat biopsy to obtain a larger or better-quality tissue sample. This delay can impact treatment timing, so it is important to discuss potential re-biopsy scenarios with your care team before the initial procedure.
PD-L1 expression can fluctuate due to tumor heterogeneity, treatment effects, or disease progression. While a single biopsy is often sufficient for initial treatment planning, your oncologist may recommend re-biopsy if your cancer progresses on immunotherapy or if you switch to a different line of therapy. This ensures the current tumor biology still matches the chosen treatment, as a tumor that was previously positive might become negative, or vice versa.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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