Onkológia 1/2016

PET/CT using 18-fluorodihydroxyphenylalanine in neuroendocrine tumours according to their types

Amino acid analogue 18-fluorodihydroxyphenylalanine (FDOPA) is a tracer of catecholamine metabolic pathway for functional imaging with positron emission tomography (PET). Diagnostic target for functional imaging of NET is a pathologically increased catecholamine or glucose metabolism or pathologically increased expression of somatostatin receptors, variably present according to type of NET. Due to heterogeneity of origin and biological properties of NET, there is no universal radiopharmaceutical permitting sufficient diagnostic accuracy of functional imaging NET of all types and of all grades of differentiation. However, the accurate staging is essential for optimal therapeutic management of NET. Diagnostic accuracy of functional nuclear medicine imaging relies upon the expression of diagnostic target by NET lesions, upon optimal choice of the tracer of diagnostic target and upon the technical performance of imaging. Commonly available comparators of FDOPA in NET are labelled somatostatin analogues for conventional scintigraphy and for PET, tracer of catecholamine synthesis and storage into secretory granules for conventional scintigraphy (123I-metaiodobenzylguanidine) and marker of glucose metabolism for PET (18-fludeoxyglucose). FDOPA shows better performances than comparators in medullary thyroid cancer, in well-differentiated catecholamine producing NETs, in well differentiated NET of mid-gut origin and in case of congenital hyperinsulinism in infants. Article summarises the documented indications of FDOPA according to type of NET and for each of them proposes currently the most performing sequence of functional imaging permitting the most accurate staging.

Keywords: neuroendocrine tumours, PET/CT, 18-fluorodihydroxyphenylalanine, somatostatin analogues, 18-fludeoxyglucose, 123I-metaiodobenzylguanidine