Inhibitors of immune checkpoints (ICIs), such as the cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), programmed cell death protein-1 (PD-1), and its ligand programmed death-ligand 1 (PD-L1), are increasingly used for the treatment of metastatic cancers (1). Here, PDCD1 is linked to metastatic malignant neoplasm.