This manuscript comprehensively reviews the evolving role of biomarkers in immunotherapy efficacy, spanning from blood-derived indicators—alpha-fetoprotein, inflammatory markers, cytokines, circulating tumor cells, and their DNA—to tissue-derived indicators—programmed cell death ligand 1 expression, tumor mutational burden, microsatellite instability, and tumor-infiltrating lymphocytes. Here, CD274 is linked to neoplasm.