The idea of using a targeting molecule that is radioactively labeled with a diagnostic radionuclide for positron emission tomography or single photon emission computed tomography imaging with the potential to show that tumoricidal radiation can be delivered to tumoral sites by administration of the same or a similar targeting molecule that is radioactively labeled with a therapeutic radionuclide called “theranostics.” For somatostatin receptor-positive, well-differentiated (neuro-)endocrine neoplasms (NENs), peptide receptor radionuclide therapy (PRRT) using radiolabeled somatostatin analogs (SSAs) is a well-established second/third-line theranostic therapy. 

In 2017 and 2018, the regulatory authorities authorized PRRT using 177Lu-DOTATATE for a subset of patients with low-grade, well-differentiated gastroenteropancreatic (GEP) NENs. It enhanced the quality of life and progression-free survival of GEP NEN patients. In addition, individuals with functional metastatic GEP NENs, including metastatic insulinomas, Verner Morrison syndromes (VIPomas), glucagonomas, gastrinomas, and patients with carcinoid disease, also showed favorable clinical and biochemical responses to PRRT using 177Lu-DOTATATE. 

Inoperable low-grade bronchopulmonary NENs, paragangliomas, pheochromocytomas, and medullary thyroid carcinomas may all benefit greatly from the treatment in the future. Presently being researched were first-line PRRT using 177Lu-DOTATATE and combinations of the treatment with cytotoxic medicines. SSAs combined with radionuclides that release alpha radiation and somatostatin receptor antagonists coupled with radionuclides were two examples of new radiolabeled somatostatin receptor ligands.