GRPR and gastrin-producing neuroendocrine tumor: Moreover, over-expression of GRPR was reported in other cancers, among the most relevant for use of a GRPR targeting radiotherapy are gastrinomas (about 100% express GRPR), gastrointestinal stromal tumors (GIST, about 85%) and estrogen receptor positive breast cancer (over 80%) (Cornelio et al. 2007; Dimitrakopoulou-Strauss et al. 2007; Morgat et al. 2017; Reubi et al. 2004; Reubi et al. 2002).