An artificial intelligence‐powered PD‐L1 combined positive score (CPS) analyser in urothelial carcinoma alleviating interobserver and intersite variability

Abstract

AimsImmune checkpoint inhibitors targeting programmed death‐ligand 1 (PD‐L1) have shown promising clinical outcomes in urothelial carcinoma (UC). The combined positive score (CPS) quantifies PD‐L1 22C3 expression in UC, but it can vary between pathologists due to the consideration of both immune and tumour cell positivity.Methods and ResultsAn artificial intelligence (AI)‐powered PD‐L1 CPS analyser was developed using 1,275,907 cells and 6175.42 mm2 of tissue annotated by pathologists, extracted from 400 PD‐L1 22C3‐stained whole slide images of UC. We validated the AI model on 543 UC PD‐L1 22C3 cases collected from three institutions. There were 446 cases (82.1%) where the CPS results (CPS ≥10 or <10) were in complete agreement between three pathologists, and 486 cases (89.5%) where the AI‐powered CPS results matched the consensus of two or more pathologists. In the pathologist's assessment of the CPS, statistically significant differences were noted depending on the source hospital (P = 0.003). Three pathologists reevaluated discrepancy cases with AI‐powered CPS results. After using the AI as a guide and revising, the complete agreement increased to 93.9%. The AI model contributed to improving the concordance between pathologists across various factors including hospital, specimen type, pathologic T stage, histologic subtypes, and dominant PD‐L1‐positive cell type. In the revised results, the evaluation discordance among slides from different hospitals was mitigated.ConclusionThis study suggests that AI models can help pathologists to reduce discrepancies between pathologists in quantifying immunohistochemistry including PD‐L1 22C3 CPS, especially when evaluating data from different institutions, such as in a telepathology setting.