Аннотация
Relevance: Bladder cancer is one of the most common malignancies and is characterized by frequent recurrences, marked biological heterogeneity, and an unfavorable prognosis following progression to muscle-invasive and metastatic disease.The study aimed to investigate the clinical and biological significance of programmed death-ligand 1 (PD-L1) expression in bladder cancer in relation to the characteristics of the tumor microenvironment and antitumor immune response, as well as to determine its prognostic and predictive value for patient stratification and prediction of immunotherapy efficacy, taking into account the existing controversies regarding the assessment of this biomarker.Materials and Methods: This study was conducted as a systematic literature review in accordance with the PRISMA 2020 guidelines. A literature search was performed in the PubMed, Scopus, and Web of Science databases for publications published between 2016 and 2025 using the following keywords and their combinations: “PD-L1,” “urothelial bladder cancer,” “immune checkpoint inhibitors,” “tumor microenvironment,” and “CD8+ T-lymphocytes.” Original studies and meta-analyses investigating PD-L1 expression in urothelial bladder cancer, its association with tumor morphological characteristics, molecular subtypes, tumor microenvironment parameters, and its prognostic and predictive significance were included in the analysis.Results: The analysis of the available literature demonstrated that immune checkpoint hyperexpression is associated with unfavorable clinicopathological features of bladder cancer, including muscle-invasive tumor growth, advanced disease stage, and high histological grade (OR = 3.67). At the same time, PD-L1 hyperexpression was associated with a better response to immunotherapy; however, clinical benefit may also be observed in patients with low or negative PD-L1 expression.Conclusion: The findings confirm the important role of PD-L1 status in shaping the immune tumor microenvironment and the biological behavior of urothelial bladder cancer. Considering PD-L1 expression levels together with the molecular subtype may improve patient stratification and optimize immunotherapy selection. Further studies are warranted to standardize PD-L1 assessment methods and to clarify its clinical significance.