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Test Description
PD-L1 Marker (Programmed Death-Ligand 1) is a protein that plays a critical role in the immune system’s ability to fight cancer. It is expressed on the surface of tumor cells and can inhibit T-cell activation, allowing cancer cells to evade immune detection. Testing for PD-L1 levels in tumor tissue helps determine whether patients may benefit from immunotherapy, particularly immune checkpoint inhibitors that target the PD-1/PD-L1 pathway.
Indications of PD-L1
PD-L1 testing is primarily indicated for patients diagnosed with certain types of cancer, including:
- Non-small cell lung cancer (NSCLC)
- Melanoma
- Hodgkin lymphoma
- Bladder cancer
- Kidney cancer
- Breast cancer
- Head and neck cancers
- Gastric and cervical cancers
The test helps inform treatment decisions regarding the use of immunotherapy, especially when other targeted therapies are not available.
Patient Preparation/Instructions
Patients typically do not require special preparation before undergoing a PD-L1 test. The test is performed on a sample of tumor tissue, which may be obtained through:
- Surgical removal of the tumor
- A biopsy procedure
If a biopsy has already been performed for diagnosis, the same sample can be used for PD-L1 testing.
The results of PD-L1 testing are reported as a percentage of tumor cells expressing PD-L1:
- Negative: Less than 1% expression
- Low Positive: 1% to 49% expression
- High Positive: 50% or greater expression
Higher levels of PD-L1 expression generally indicate a greater likelihood of responding to immunotherapy.
