While traditional chemotherapy and targeted therapies have limited long-term effectiveness, checkpoint inhibitors like PD-1 (programmed cell death protein 1), a receptor on T cells that regulates immune responses, and PD-L1 (programmed death-ligand 1), a protein expressed on tumor cells that helps them evade immune detection, have shown promise by improving response and survival rates. This evidence concerns the gene PDCD1 and neoplasm.