This review synthesizes cutting-edge peripheral blood testing achievements for predicting PD-1/PD-L1 immunotherapy response, encompassing tumor-derived biomarkers (circulating tumor cell, circulating tumor DNA, blood tumor mutation burden, etc.), multidimensional immune profiling (lymphocyte count, neutrophil-to-lymphocyte ratio, T/B/NK/myeloid subsets, cytokines), and multi-parameter models. The gene discussed is PDCD1; the disease is neoplasm.