PDL1 IHC Marker

Function

Programmed Death-Ligand 1 (PD-L1) is a protein that acts as a 'brake' to keep the body’s immune responses in check. Some cancer cells produce high amounts of PD-L1 to hide from the immune system’s T-cells. Immunohistochemistry (IHC) is a laboratory technique used to visualize the expression of this protein on the surface of tumor cells.

Why it is Ordered

This test is a 'companion diagnostic' used to determine if a patient is a candidate for immunotherapy, specifically immune checkpoint inhibitors like Pembrolizumab (Keytruda) or Nivolumab (Opdivo). It is commonly ordered for:

• Non-Small Cell Lung Cancer (NSCLC)
• Urothelial Carcinoma
• Triple-Negative Breast Cancer
• Gastric and Esophageal Cancers

Associated Conditions

PD-L1 testing is relevant in various malignancies where the immune system's ability to recognize the tumor is compromised. The result is typically reported as a Tumor Proportion Score (TPS) or Combined Positive Score (CPS), which reflects the percentage of cells staining positive for the marker.

High expression of PD-L1 often correlates with a higher likelihood of responding to specific immunotherapy drugs, which can significantly improve survival outcomes compared to traditional chemotherapy in certain patient populations.