ECP 2025 – High inter-observer agreement and determination of the training effect in the CPS assessment of PD-L1 in different Indications

Immunohistochemical testing for programmed cell death-ligand 1 (PD-L1) has proven to be a useful predictive marker for anti-PD-1 therapy. Tumor cells (TC) and/or tumor-associated immune cells (TAIC) are used to determine the level of PD-L1 expression often detected using the PD-L1 IHC 22C3 pharmDx. Samples are either evaluated by the Tumor Proportion Score (TPS: TC PD-L1 staining) or by the Combined Positive Score (CPS: PD-L1 TC and TAIC staining).