PDCD1 and neoplasm: Anti-PD-1/PD-L1 antibodies to treat metastatic NSCLC first entered the clinic in 2015 based on the CheckMate 017 trial.102 Then, pembrolizumab and atezolizumab also received regulatory approval in previously treated metastatic NSCLC patients.103,104 The results of CheckMate 032 have shown impressive response rates for the nivolumab and nivolumab/ipilimumab arms in relapsed small-cell cancer.105 However, immunotherapy is only effective for a small percentage of cancer patients, and the complexity of the tumor immune microenvironment may account for this phenomenon.