Peptide receptor imaging and therapy

This article reviews the results of somdostatin receptor imaging (SRI) in p atients with somatostatin receptor-positive neuroendocrine tumors, such as pituitary tumors, endocrine pancreatic tumors, carcinoids, gastrinomas, and paragangliomas, or other diseases in which somatostatin receptors may also be expressed, like sarcoidosis and autoimmune diseases. [In-111-DTPA(0)]oc treotide is a radiopharmaceutical that has great potential for helping visu alize whether somatostatin receptor-positive tumors have recurred. The over all sensitivity of SRI to localize neuroendocrine tumors is high. In severa l neuroendocrine tumor types, inclusion of SRI in the localization or stagi ng procedure may be very rewarding in terms of cost effectiveness, patient management, or quality of life. The value of SRI in patients with other tum ors, such as breast cancer or malignant lymphomas, or in patients with gran ulomatous diseases has to be established. The application of radiolabeled p eptides may be clinically useful in another way: after the injection of [In -111-DTPA(0)]octreotide, surgeons can detect tumor localizations by a probe that is used during the operation. This may be of particular value if smal l tumors with a high receptor density are present (e.g., gastrinomas). As t he success of peptide receptor scintigraphy for tumor visualization became clear, the next logical step was to try to label these peptides with radion uclides emitting alpha or beta particles, or Auger or conversion electrons, and to perform radiotherapy with these radiolabeled peptides, The results of the described studies with Y-90- and In-111-labeled octreotide show that peptide receptor radionuclide therapy using radionuclides with appropriate particle ranges may become a new treatment modality. One might consider th e use of radiolabeled somatostatin analogs first in an adjuvant setting aft er surgery of somatostatin receptor-positive tumors to eradicate occult met astases and second for cancer treatment at a later stage.