Emerging evidence indicates that the failure of anti-PD-1 in cancer treatment partly results from the imbalance between CD8+ T cells and tumor burden, and the therapeutic efficacy of anti-PD-1 is positively associated with the ratio of CD8+ T cell invigoration to the tumor burden (measured as the sum of the long axis of all lesions, cm) 15. This evidence concerns the gene PDCD1 and cancer.