Oral Presentation Annual Meetings of the Endocrine Society of Australia and Society for Reproductive Biology and Australia and New Zealand Bone and Mineral Society 2016

Diagnostic modalities & targeted radionuclide therapies in Phaeochromocytoma and Paraganglioma (#87)

Rod Hicks 1
  1. Peter MacCallum Cancer Centre, East Melbourne, VIC, Australia

The genomic landscape of pheochromocytoma and paraganglioma (Pheo/PGL) has potential implications for optimal imaging strategies for screening at-risk patients and for selecting optimal therapies in those known to have disease.  It is now recognized that up to a third of all Pheo/PGL arise from germ-line mutations. Although anatomical imaging, including CT, MRI and ultrasound, has been the most widely advocated approach for detection of Pheo/PGL in patients at high risk of these conditions through the documentation of heritable mutations or a relevant family history, there is increasing recognition of the opportunity to better stage and characterize disease using molecular imaging techniques. The use of radioactive tracers that target specific aspects of the biology of these tumours can have either purely diagnostic or combined diagnostic and therapeutic (“theranostic”) roles. The mainstay of functional imaging and the only tracer widely used for both the diagnosis and therapy of Pheo/PGL is meta-iodo-benzylguanidine (MIBG). A range of PET agents including I-124 MIBG, C-11 hydroxyepedrine(HED), and F-18 flurodopamine (FDA) and F -18 –L-fluoro-dihydroxyphenylalanine (FDOPA), have been shown to offer diagnostic advantages compared to standard nuclear medicine imaging. These agents are, however, not widely available. Although non-specific, increased glycolytic metabolism has been shown to be a feature of many Pheo/PGL, especially those arising within the pseudo-hypoxia cluster. With the wide clinical availability of FDG PET/CT, this has become a practical alternative to I-123 MIBG SPECT/CT for detection and staging of these tumours. Recognition of the frequent expression of somatostatin receptors (SSTR) on Pheo/PGL has also led to the use of radiolabelled somatostatin analogues (SSA) for both diagnosis and therapy. Various SSAs have been labelled for PET imaging and also with therapeutic radionuclides, representing an alternative theranostic paradigm to that offered by I-124/I-131 MIBG. Peptide receptor radionuclide therapy (PRRT) is an emerging therapy for metastatic disease.