To the Editor We read with great interest the article by Duan et al1 focusing on the assessment of the efficacy and safety profile of anti–programmed cell death 1 (PD-1) and anti–programmed cell death ligand 1 (PD-L1) immunotherapy by a mirror-principle meta-analytical method. With growing numbers of anti–PD-1 and anti–PD-L1 immunotherapy agents alone or in combination approved by the US Food and Drug Administration and other international regulatory agencies, and many similar drugs in various phases of clinical development, the goal of this study is indeed important for clinicians to select appropriate therapeutic regimens for patients with cancer. The authors of this study1 concluded that the efficacy of anti–PD-1 immunotherapy is superior to that of anti–PD-L1 immunotherapy with respect to overall and progression-free survival. In addition, there appears to be no significant difference in their respective safety profiles.