The most profound decrease (> 98%) was observed in the GIST tumor (0.3 ± 0.1 vs 19.1 ± 3.9% ID/g) and the pancreas (0.1 ± 0.0 vs 8.5 ± 2.0% ID/g) (Figure 2A), indicating GRPR specificity. This evidence concerns the gene GRPR and gastrointestinal stromal tumor.