Somatostatin receptor targeting for tumor imaging and therapy.

Somatostatin receptors and their ligands constitute the prototype targeting system for contrast-enhanced detection and radiotherapy of cancer. Radiolabeled synthetic analogs of somatostatin have been successfully used in routine molecular imaging of primary gastroenteropancreatic neuroendocrine tumors and their metastases for more than 15 years. Likewise, analog conjugates for radiation therapy have been developed and have been under clinical trial for several years. The vast amount of knowledge accumulated by both basic and clinical science has made the somatostatin/somatostatin receptor system a popular model for new targeting strategies in imaging and therapy. Among those, the use of near-infrared fluorescent dye-peptide conjugates for the detection of tumors by endoscopy, mammography, or intraoperative imaging is one of the most promising. This article reviews recent developments in the field and discusses concepts for receptor-targeted molecular imaging and therapy.