GRPR and neoplasm: In PC3-mice, it demonstrated high and specific tumor uptake (45.4 ± 3.9 and 4.9 ± 1.6% I.A./g at 4 and 96 h p.i., respectively), while lower GRPR density in T47D-mice led to reduced uptake (6.1 ± 3.9 and 0.7 ± 0.1% I.A./g at 4 and 72 h p.i.).