Currently available markers that can be measured in peripheral blood include total monocyte count, myeloid-derived suppressor cells (MDSCs), regulatory T cells (Tregs), relative eosinophil count, cytokine levels (such as IL-6, IL-8, and IL-10), lactate dehydrogenase (LDH), C-reactive protein (CRP), soluble forms of CTLA-4 and PD-1 or PD-L1, as well as circulating tumor DNA (ctDNA). This evidence concerns the gene PDCD1 and neoplasm.