Onkológia 5/2017

Indications for PET/CT with individual radiopharmaceuticals according type of neuroendocrine neoplasm

The functional imaging of NEN lesions using PET/CT with tracers of metabolism (FDOPA and FDG) and with tracers of somatostatin receptor expression (somatostatin analogues labelled with gallium (68Ga)) is currently an important tool for characterisation and localisation of their lesions and has brought an important progress in their therapeutic management. Functional imaging of somatostatin receptor expression by NEN lesions using gallium (68Ga) labelled somatostatin analogues allows, in addition to localization of their lesions, also identification of the target for treatment with non-radioactive and radioactive somatostatin analogues. Inversely, FDOPA and FDG are not the theranostic radiopharmaceuticals. The choice of an optimal radiopharmaceutical for functional imaging of NEN lesions using PET/CT depends upon the NEN type, its usual biological properties and clinical situation in which the examination is indicated. FDOPA is the optimal radiopharmaceutical for localisation of lesions of medullary thyroid cancer in case of rising serum calcitonin levels, for characterisation and localisation of lesions of pheochromocytoma and paraganglioma, for characterisation and localisation of lesions of midgut-NEN, and in differential diagnosis of focal or diffuse form of hyperinsulinism in infants and children. Somatostatin analogues labelled by gallium (68Ga) are optimal for characterization and localization of lesions of foregut-NEN. FDG is currently the most frequently used radiopharmaceutical for PET in oncology; however, even if NEN is not a part of its documented indications, FDG may be helpful in localisation of poorly differentiated biologically aggressive forms of NEN and in localisation of synchronous or metachronous non-NEN malignancy; FDG uptake by NEN lesions is considered as an unfavourable prognostic feature. Current recommended indications for PET/CT with different radiopharmaceuticals in NEN take into consideration the diversity of their origin, localisation and biological properties. The aim of the article is to assist the clinicians to optimise individually adapted diagnostic and therapeutic workup considering the clinical situation of given patient with known or suspected NEN.

Keywords: PET/CT, somatostatin analogue labelled by (68Ga), FDOPA, FDG, neuroendocrine neoplasm, medullary cancer of thyroid gland, pheochromocytoma, paraganglioma, foregut, midgut, hindgut, hyperinsulinism in infants