First Experience Using ¹⁸F-Flubrobenguane PET Imaging in Patients with Suspected Pheochromocytoma or Paraganglioma

Abstract

Rationale: Pheochromocytomas and paragangliomas are a rare tumor entity originating from adreno-medullary chromaffin cells in the adrenal medulla or in sympathetic, paravertebral ganglia outside the medulla. Especially small lesions are difficult to detect by conventional CT or MR imaging and even by SPECT imaging with currently available radiotracers (e.g. MIBG). The novel PETradiotracer F-18-flubrobenguane could change the diagnostic paradigm in suspected pheochromocytomas and paragangliomas due to its homology to MIBG and the general advantages of PET-imaging. Aim of this retrospective analysis was to evaluate F-18-flubrobenguane in pheochromocytomas and paragangliomas and to investigate the biodistribution in patients. Methods: 24 Patients with suspected pheochromocytoma and paraganglioma underwent PET/CT or PET/MRI at 63±24 min p.i. after injection of 256±33 MBq F-18-flubrobenguane. SUVmean and SUVmax values of organs were measured with spherical volume-of-interests. Threshold segmented volume-of-interests were used to measure SUVmean/max of the tumor lesions. One reader evaluated all crosssectional imaging datasets (CT or MRI) separately as well as the PET hybrid datasets and reported lesion number and size. A three point-scale indicating the diagnostic certainty for a positive lesion was assigned.

Diagnostic Performance of 124I-Metaiodobenzylguanidine PET/CT in Patients with Pheochromocytoma

“…Due to superior technology and workflows, Positron Emission Tomography (PET) expanded rapidly (6) and is now standard imaging modality for most cancer entities including pre-therapeutic imaging in patients with NET (7) and Prostate Cancer (8,9). In patients with pheochromocytoma and paraganglioma somatostatin receptor-targeted PET (10-12) and 18 F-Flubrobenguane (13) have shown a high specific uptake and a high sensitivity. However, 124 I-MIBG PET comes with several potential advantages:…”

Imaging pheochromocytoma in small animals: preclinical models to improve diagnosis and treatment

“…After this preclinical proof-of-concept study in the MENX rats and a phase I study in healthy humans assessing human safety, whole-organ biodistribution and radiation dosimetry [ 75 ], [ 18 F]-LMI1195 was evaluated in a retrospective study of 24 patients with suspected PPGLs. Patients scans were performed between 2016 and 2018, and the data were recently published [ 76 ]. The highest SUV could be observed in thyroid, pancreas and tumor lesions, with unaffected adrenal glands and liver parenchyma having significantly lower SUV compared to the tumors.…”

“…The hybrid detection of [ 18 F]-LMI1195 PET and CT/MRI detected more and smaller lesions than conventional imaging, but this did not reach statistical significance probably due to the low patient number. However, diagnosis confidence and detection size was better in [ 18 F]-LMI1195 PET/CT/MRI than CT/MRI alone [ 76 ]. The data strongly speaks for further evaluation of this tracer in larger patient cohorts and a comparison with the gold standard MIBG SPECT/CT.…”

Hybrid imaging of neuroendocrine tumors in the heart: Union is strength

“…SDHx mutations are also associated with reduced PNMT expression (leading to a noradrenergic profile) and increased SSTR-2 expression, which can be utilized by somatostatin receptor tracers, for example 68 Ga-DOTATATE. 18 Fdihydroxyphenylalanine (DOPA) PETs also have very good diagnostic value in SDHx mutation carriers, 60 which suggests a possibly larger role in the imaging of cardiac PGLs. Consequently, 18 F-FDG PET may be the most valuable functional imaging modality for the evaluation of patients with cardiac PGLs, for MEN2associated PHEOs and for the detection of metastases.…”

“…However, a relative limitation of 18 F-FDOPA is the potential for false-negative scans in individuals with cluster 1a SDHx-related PPGLs. 60 SDHx-related PGLs, may undergo MRI every 1-5 years, while 68 Ga-DOTA-TATE PET/CT is often used at baseline (and periodically) to define the extent of disease more accurately, given its greater sensitivity. 61,62 There are also cases where 18 F-FDG PET/CT showed hypermetabolism of the tumoral cells whereas no uptake of the radiotracer 123 I-MIBG scans, was revealed.…”