PET/CT in Neuroendocrine Tumors: Evaluation of Receptor Status and Metabolism

In-111 Octreoscan is considered the gold standard for imaging of neuroendocrine tumors (NET). However, in the absence of morphologic imaging correlation, the exact localization of the tumor is often difficult. Also the sensitivity of PET imaging is more than Gamma camera (SPECT) imaging. Ga-68 labeled somatostatin analogs (SMS-R) are interesting radiopharmaceuticals for PET receptor imaging of NET. Some other radiopharmaceuticals e.g. F-18 DOPA can also be used to assess metabolism and functional status of NET. The importance of these radiopharmaceuticals, especially SMS-R increases in the absence of any specific biochemical marker or clinical parameter for follow-up of patients after therapy (eg. peptide receptor radionuclide therapy, surgery, chemoembolisation, etc). New criteria based on molecular, metabolic and morphologic imaging needs to be developed for correct assessment of response to therapy for these slow-growing, solid tumors.