In particular, we focus on electrochemical immunosensors for the detection of multiplex tumor biomarkers in human serum (e.g., carcinoembryonic antigen (CEA), alpha-fetoprotein (AFP), carcinoma antigen 125 (CA125), cancer antigen 15-3 (CA 15-3), apolipoprotein A1 (ApoA1), and cytokines) based on the use of PB deposited on graphene, carbon nanotubes, quantum dots, magnetic particles, and gold nanoparticles as novel strategies for improved early tumor diagnostics. This evidence concerns the gene CEACAM5 and neoplasm.