PDCD1 and neoplasm: However, another meta-analysis revealed that PD-L1 expression in NPC did not correlate with OS, and no statistically significant differences existed between the expression level of PD-1 in tumor infiltrating lymphocytes (TILs), which indicated that higher/positive expression of PD-L1/PD-1 may not serve as suitable biomarkers for the prognosis of NPC 12.