Treatment with PA induced a drastic increase in tumor values for both radiotracers with 99mTc-N4-GRP(14–27) showing superior tumor values than the shorter chain 99mTc-N4-GRP(18–27) (38.19 ± 4.79%ID/g vs. 28.37 ± 8.05%ID/g, respectively; p < 0.01). The gene discussed is GRP; the disease is neoplasm.