Inter-Rater Agreement in PD-L1 (22C3) Expression Evaluation in Colon Cancer

Abstract

Programmed death-ligand 1 (PD-L1) is a predictive biomarker in various cancers. In colorectal cancer, PD-L1 expression evaluation is not part of the routine examination and standardized evaluation methods are lacking. This study aimed to examine inter-rater agreement in PD-L1 expression evaluation in patients with colon cancer (CC) using different manual scoring methods, and to compare the manual methods to a digital evaluation. Two pathologists evaluated 188 PD-L1-stained slides from patients with CC. The tumor proportion score (TPS) and immune cell score (ICS) were categorized as