Abstract
OBJECTIVE: To summarise the current evidence of the significance and prognostic value of programmed cell death protein ligand 1 (PD-L1) expression in patients with non-muscle-invasive bladder cancer (NMIBC) treated with bacille Calmette-Guérin (BCG) immunotherapy. METHODS: A search was conducted in May 2020 of three electronic databases; MEDLINE, Scopus, and EMBASE. In this review we included results from original studies investigating the relationship between the PD-L1 expression and BCG response in patients with NMIBC. RESULTS: Only five relevant articles were identified in the literature to date. Some studies showed an association between increased PD-L1 expression and BCG unresponsiveness; however, other authors provided contradictory results and suggested that PD-L1 evaluation could not be used for reliable prediction of BCG response. CONCLUSIONS: The value of PD-L1 evaluation in predicting BCG response is debatable. Current evidence, based only on retrospective analyses, is inconsistent. Comparability of the results is diminished by the methodological limitations of immunohistochemistry assessment. Further multicentre, randomised trials are needed to make definitive conclusions. ABBREVIATIONS: ICs: immune cells; IHC: immunohistochemical staining; (N)MIBC: (non-) muscle-invasive bladder cancer; PD-L1: programmed cell death protein ligand 1; PD-1: programmed cell death protein 1; RC: radical cystectomy; TCs: tumour cells.