PDL1positiva

PD-L1 positivity refers to the expression of the programmed death-ligand 1 (PD-L1) protein on the surface of cells, typically tumor cells and/or infiltrating immune cells, as detected by immunohistochemistry (IHC). PD-L1 binds to the PD-1 receptor on T cells, delivering an inhibitory signal that can weaken anti-tumor immune responses.

In oncology, PD-L1 expression is used as a predictive biomarker for response to immune checkpoint inhibitors that target PD-1 or PD-L1. Testing may guide treatment decisions in several cancers, but it is not a perfect predictor: responses can occur in PD-L1–negative tumors, and not all PD-L1–positive tumors respond.

Assessment methods vary by indication and drug. Common metrics include the tumor proportion score (TPS), the percentage of PD-L1–staining tumor cells, and the combined positive score (CPS), which includes PD-L1 staining of both tumor and certain immune cells relative to total viable tumor cells. Thresholds differ by cancer type and therapy. Different IHC assays (such as 22C3, 28-8, SP263, SP142) are used as companion diagnostics for specific drugs.

Biological and technical considerations affect testing. PD-L1 expression can be heterogeneous within a tumor and may change over time or with therapy. Pre-analytic factors, tissue type, and staining protocols influence results. Therefore, PD-L1 status should be interpreted in the clinical context and in conjunction with validated, indication-specific assays.