Tumor-related markers such as CEA and CYFRA21-1 [23], CTCs [39, 40] and PD-L1+ CTCs [43], together with selected immune subsets including CD73+ PD-1+ CD8+ T cells [89] and CD26highCD4 +T cells [110], have been prospectively evaluated and reached level-2A evidence. This evidence concerns the gene PDCD1 and neoplasm.