Numerous tracers have been produced and evaluated for PCa, which can be divided into three subcategories: (i) imaging agents that are used to detect cell division activity (e.g., choline, acetate, glucose, and amino acids); (ii) radiolabeled molecules that are used to target cancer-specific membrane proteins or receptors, e.g., ligands that bind to androgen receptors (ARs), prostate-specific membrane antigen (PSMA), or gastrin-releasing peptide receptors (GRPRs); and (iii) compounds that specifically bind to bone metastases [13]. This evidence concerns the gene GRPR and cancer.