Diagnostic Pd-L1 Immunohistochemistry In Nsclc: Results Of The First German Harmonization Study

3028Background: Immunohistochemistry for PD-L1 (PD-L1 IHC) may be predictive for anti-PD-1 and anti-PD-L1 immunotherapy in non-small cell lung cancer (NSCLC). Several PD-L1 IHC assays with individual reagents and scoring-criteria are developed in parallel. Biomarker testing and clinical decision making would profit from one harmonized u0027PD-L1 statusu0027. Methods: Fifteen NSCLC resection specimens were centrally stained with the PD-L1 IHC assays 28-8, 22C3, SP142 and SP263. The slides were scored by nine German pathologists. Proportions of PD-L1 positive tumor cells (TC) and immune cells (IC) were scored according to a 6-step scoring system that integrates all cut-off criteria employed by the four assays. Interobserver and interassay concordance were analyzed with u0027Ru0027 Version 3.2.3. Results: Proportion-scoring of PD-L1 positive TC showed moderate interobserver concordance coefficients for the 6-step scoring system as well as a simplified 6-step score (Lightu0027s kappa = 0.4 - 0.5). The integrated dichotomous prop...