GRPR and prostate adenocarcinoma: Amongst several analogs developed and preclinically screened in our studies, [99mTc]Tc-DB7 (DB7, N4-PEG2-DPhe-Gln-Trp-Ala-Val-Gly-His-Leu-NHEt; PEG2, 8-amino-3,6-dioxaoctanoic acid; Figure 1a) displayed GRPR-specific uptake in human prostate adenocarcinoma PC-3 xenografts in mice (4.49 ± 1.20%IA/g at 4 h post-injection, pi) vs. a very low background, even from the GRPR-rich pancreas (0.56 ± 0.20%IA/g at 4 h pi), featuring qualities that favor high-contrast imaging with SPECT [36].