Clinical relevance of PD-L1 expression in gallbladder cancer: a potential target for therapy.

Aims: Programmed death-ligand 1 (PD-L1), a potential target for immune checkpoint inhibitors in various solid neoplasms, has been studied in very few cases of Gall Bladder Carcinoma (GBC). The current study aimed to evaluate PD-L1 expression at primary and metastatic sites of GBC, and its associations with standard prognostic clinicopathological parameters, as well as with overall survival.

Methods And Results: One hundred and seventy-four cases of GBC were evaluated for PD-L1 expression by the use of the SP263 clone in tissue microarrays. Clinicopathological characteristics and survival data were correlated with PD-L1 expression analysed at different cut-offs of ≥1%, ≥10% and ≥50% in tumour cells and tumour-infiltrating lymphocytes (TILs). The mean age of patients was 49.9 years, and the male/female ratio was 1:2.9. Of the cases, 73.6% presented with stage 3/4 disease. Tumour cells expressed PD-L1 in 23.0% of cases, and TILs expressed PD-L1 in 24.1% of cases. At a cut-off of 10%, 14.9% of cases expressed PD-L1, and at a cut-off of 50%, 7.5% of cases expressed PD-L1. Significant associations were seen between tumour proportion score and histological type (P = 0.004), histological grade (P = 0.004), nuclear grade (P = 0.008), nodal metastasis (P = 0.051), higher stage (P = 0.058), and TILs (P < 0.001). Tumour size, growth pattern, the presence of necrosis and lymphovascular emboli showed no significant associations with PD-L1 in tumour cells or TILs. In synchronous paired samples from primary and metastatic lymph nodes, discordantly higher PD-L1 expression was evident in lymph nodes. Overall survival was not associated with PD-L1 expression (P = 0.546).

Conclusion: PD-L1 does not appear to be a prognostic marker or influence survival in GBC patients. However, PD-L1 expression occurs in one of four GBCs, supporting the future possibility of immune-modulation therapy to improve the dismal overall survival.