CCKBR and medullary thyroid gland carcinoma: A highly promising molecular target to develop radiopeptides for diagnostic imaging and targeted radiotherapy (TRT) of medullary thyroid carcinoma (MTC), small cell lung cancer (SCLC), astrocytoma, stromal ovarian cancer, as well as carcinoids and other tumors of neuroendocrine origin is the cholecystokinin-2 receptor (CCK2R) as an increased level of expression is observed in these malignancies [5,6].