Biomarkers for predicting responses to immune checkpoint inhibitors such as cancer gene alterations and immune responses have been extensively investigated using patients’ tumor and blood samples.44–47 In this study, we demonstrated that palmitic and palmitoleic acid levels and ratio of palmitoleic/palmitic acid in the sera of NSCLC patients at baseline were inversely correlated with the responses and prognosis including PFS and OS of patients treated with anti-PD-1 antibody and could be predictive biomarkers for PD-1/PD-L1 based immunotherapy. The gene discussed is PDCD1; the disease is cancer.