While circulating PD-L1-expressing myeloid populations are less well documented than the factors described above, it has been reported that, in lung cancer, treatment with PD-1/PD-L1 blockade response correlated with systemic PD-L1+ CD11b+ myeloid cell frequency, suggesting a potential for stratification based on systemic PD-L1+ myeloid cell subsets [37]. This evidence concerns the gene ITGAM and lung cancer.