The following factors are expected to be biomarkers for predicting the efficacy of ICI treatment: cytokines in the tumor microenvironment; tumor infiltrating lymphocytes (TILs) and associated macrophages; and immune checkpoint proteins, such as programmed cell death-1 (PD-1), programmed cell death ligand-1 (PD-L1), cytotoxic T-lymphocyte associated protein 4 (CTLA-4), and major histocompatibility complex (MHC) (12, 13). Here, PDCD1 is linked to neoplasm.