Radiometal-labeled somatostatin analogs for applications in cancer imaging and therapy

The use of radiolabeled peptides for the diagnosis and therapy of cancer has increased greatly over the last few decades. Skillfully crafted peptide systems, which have high affinity for receptors that are overexpressed in human tumors, offer the potential to improve the characterization, grading, and eventual therapy of human cancer. Robust peptide systems can be labeled with radioactive atoms for imaging purposes using single-photon emission computed tomography and positron emission tomography technologies, or can be labeled with therapeutic nuclides for the efficient killing of tumor cells. This method-based review discusses one such class of receptor-targeted peptides and their radiolabeling with radioactive metals. The somatostatin receptor is upregulated in many types of cancer, and when labeled with a radiometal atom via a bifunctional chelate, can be employed as an agent for the imaging and radiotherapy of cancer. This review will discuss the methods used in the synthesis of the somatostatin peptides, conjugation with bifunctional chelators, and radiolabeling with metal radionuclides. Methods will also be presented for the in vitro and in vivo evaluation of the compounds produced.