GRPR and prostate cancer: The first cobalt-55 imaging of GRPR was reported in 2016 by Dam et al. [111] and compared 55Co-, 57Co-, and 68Ga-labeled GRPR agonist NOTA-AMBA (NOTA-Gly-4-ABz-Gln-Trp-Ala-Gly-His-Leu-Met-NH2) in a PC3 prostate cancer.