Tin-117m somatoostatin analogs or antagonist are used to treat tumors and symptoms associated with these tumors which express somatostatin receptors, such as gastroenteropancreatic neuroendocrine tumors. The tin-117m somatostatin receptor binding compounds can be administered at a dosage which is effectively apoptotic and not necrotic. Also, if desired, it can be administered at a dose that is necrotic and/or induces necrosis, but only to cells within 290 microns of the tin-117m atom. A novel somatostatin analog is also disclosed, as well as novel methods to produce the tin labeled analogs and antagonists.
