Functional Imaging and Peptide Receptor Radionuclide Therapy for Pancreatic Neuroendocrine Tumor

Abstract

Somatostatin receptors (SSTR) are overexpressed in various tumors including neuroendocrine tumors. In-111 Octreoscan or Ga-68 DOTATOC positron emission tomography/computed tomography (PET/CT) showed these SSTR expressing tumors in whole body of patients. Ga-68 DOTATOC PET/CT has a better sensitivity and resolution than In-111 Octreoscan with single photon emission computed tomography (SPECT)/CT.. The indications of Ga-68 DOTATOC PET/CT are 1) staging: detect sites of primary and metastasis, 2) re-staging: follow-up of patients with known disease to detect residual, recurrent or progressive disease, 3) prognosis & management decisions: determine SSTR status & select patients with SSTR radionuclide therapy, and 4) monitor the response to therapy. Nuclear medicine treatments for neuroendocrine tumors with radioisotope labeling on the somatostatin receptor targeting peptide (peptide receptor radionuclide therapy, PRRT) were conducted in Europe, Australia, and other countries for over 20 years. Eligible patients to be effective to PRRT using Lu-177 DOTATATE can be pre-screened by confirming the expression of somatostatin receptor on tumors using Octreoscan or Ga-68 DOTATOC PET/CT prior to treatment. This pair of molecular targeted treatment and companion diagnostics, so called molecular theranostics makes PRRT a good example for a precision medicine. A multinational clinical trial with the Lu-177 DOTATATE treatment (Lutathera) showed a significant progression free survival over the control group and Ministry of Food and Drug Safety in Korea approved Lutathera. Some doctors are treating patients who are refractory to Lu-177 using Ac-225, an alpha-emitter therapy in Germany and India. The high therapeutic effect of the alpha emitting radionuclides will lead the future of nuclear medicine therapy.