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Gastrin-releasing peptide receptors (GRPRs) represent attractive targets for cancer diagnosis and therapy owing to their overexpression in widespread human tumors. Bombesin (BBN) analogues coupled to suitable chelators for stable radiometal binding have been proposed for diagnostic imaging and radionuclide therapy (theranostics) of GRPR-positive tumors. Recently, interest has shifted from BBN-like receptor agonists to GRPR-radioantagonists, because radioantagonists do not induce adverse effects after injection to patients and display superior pharmacokinetic in vivo profiles. Thus, they seem more advantageous for clinical use compared to agonists. Newer developments highlighting the theranostic potential of GRPR-radioantagonists in cancer patient management are presented herein.

Prostate cancer is the most common noncutaneous cancer among men, rendering the diagnosis and staging of significant medical and public interest. One of the most interesting developments in the application of nuclear oncology has been the development of novel diagnostic agents that are able to facilitate targeted therapies using the concept of theranostics. This review summarizes the current and emerging molecular imaging techniques for the investigation of patients with prostate cancer with emphasis on the potential of 64Cu-PSMA PET/CT in staging, restaging, and the application of theranostics.

Prostate cancer is the most common noncutaneous cancer among men, rendering the diagnosis and staging of significant medical and public interest. One of the most interesting developments in the application of nuclear oncology has been the development of novel diagnostic agents that are able to facilitate targeted therapies using the concept of theranostics. This review summarizes the current and emerging molecular imaging techniques for the investigation of patients with prostate cancer with emphasis on the potential of

Personalized dosimetry in radionuclide therapy has gained much attention in recent years. This attention has also an impact on peptide receptor radionuclide therapy (PRRT). This article reviews the PET-based imaging techniques that can be used for pretherapeutic prediction of doses in PRRT. More specifically the usage of (86)Y, (90)Y, (68)Ga, and (44)Sc are discussed: their characteristics for PET acquisition, the available peptides for labeling, the specifics of the imaging protocols, and the experiences gained from phantom and clinical studies. These techniques are evaluated with regard to their usefulness for dosimetry predictions in PRRT, and future perspectives are discussed.

In-111 Octreoscan is considered the gold standard for imaging of neuroendocrine tumors (NET). However, in the absence of morphologic imaging correlation, the exact localisation of the tumor is often difficult. Also the sensitivity of PET imaging is more than Gamma camera (SPECT) imaging. Ga-68 labelled 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.

Neuroendocrine tumors are malignant solid tumors originating from neuroendocrine cells dispersed throughout the body. Differentiated neuroendocrine tumors overexpress somatostatin receptors (SSTRs), which enable the diagnosis using radiolabeled somatostatin analogues. Internalization and retention within the tumor cell are important for peptide receptor radionuclide therapy using the same peptide. The use of the same DOTA-peptide for SSTR PET/CT using (68)Ga and for peptide receptor radionuclide therapy using therapeutic radionuclides like (177)Lu and (90)Y offers a unique theranostic advantage.

Peptide receptor radionuclide therapy involves selective targeting of neuroendocrine tumors through the somatostatin receptors, the aim being to increase radiation dose to the tumors and spare the normal tissue. The advantage of this internal radiation therapy is the ability to selectively target multiple metastases throughout the body. Early and accurate assessment of therapy response helps not only to identify the poor responders but also to personalize the treatment regimes with the aim of achieving maximum treatment benefit. This is the basis of theranostics.