PDCD1 and gastric cancer: PD-L1 was also found to be an independent prognostic factor for OS in GC patients, and a raised PD-L1/PD-1 expression was linked to a significantly improved outcome according to a study conducted by Boger et al. The study suggested that PD-L1/PD-1 expression may be used as a surrogate marker for GC patients with PD-L1 positivity, thereby guiding immunotherapy with immune checkpoint antibodies [27].