PDCD1 and non-small cell lung carcinoma: <h4>Background</h4>The efficacy of combining programmed cell death protein-1 (PD-1)/programmed death-ligand 1 (PD-L1) inhibitors with multi-targeted anti-angiogenic tyrosine kinase inhibitors (TKIs) in advanced or metastatic non-small cell lung cancer (NSCLC) remains controversial.