Expression of Programmed Cell Death-Ligand 1 (PD-L1) in Astrocytic Tumors and Its Correlation With Histopathological Grade and Proliferative Index (Ki-67): A Cross-Sectional Study

Background Multimodality therapies for gliomas are associated with poor outcomes. Tumor cells display immune evasion by activating immune checkpoint molecules such as programmed cell death-ligand 1 (PD-L1). It could be linked with the grade proliferative index (Ki-67) serving as a potential target for immunotherapy. This study aimed to investigate the expression of PD-L1 in astrocytic tumors and correlate it with histopathological grade and Ki-67. Methodology This cross-sectional analytical study was conducted in the Department of Pathology of a tertiary medical college for four years between September 2018 and August 2022. A total of 43 cases of biopsy-proven glial tumors were included in the study after obtaining informed consent from all participants whose biopsies were considered. Clinicoradiological details were documented. Hematoxylin and eosin (H&E) slides were reviewed for histopathological grade and morphology. PD-L1 expression and Ki-67 labeling Index were studied immunohistochemically, followed by the correlation of PD-L1 with clinicopathological parameters, Ki-67 LI, and patient survival was also noted. Data were compiled into Microsoft Excel (Microsoft Corp., Redmond, WA, USA) and analyzed using SPSS Statistics for Windows, Version 21.0 (IBM Corp., Armonk, NY, USA). Descriptive data were interpreted as mean, frequencies, and percentages. Spearman's rank correlation test was used to study the correlation between PD-L1 and Ki-67. Association was tested using the chi-square test. The impact of PD-L1 on the survival of patients was also investigated by Kaplan-Meier survival analysis. Results A total of 43 patients were included with 31 males and 12 females (mean age = 46.14 years). PD-L1 expression and Ki-67 LI showed a significant relationship with advanced age (p = 0.010), histological grade (p = <0.001), presence of cellular atypia (p < 0.001), necrosis (p = <0.001), and microvascular proliferation (p < 0.001). PD-L1 showed a positive correlation with Ki-67 (r_s = 0.390; p = 0.009) and shorter survival (p = 0.006). Conclusions Greater PD-L1 expression in astrocytic tumors is associated with higher grade and Ki-67 LI. Poor survival with PD-L1 positivity is likely reflective of the increased aggressiveness conferred by the PD-L1-induced immune evasion. PD-L1, a negative predictive biomarker, may serve as a novel target in immunotherapy for gliomas.