68 Ga-DOTATATE PET and functional imaging in pediatric pheochromocytoma and paraganglioma

Physiological bio-distribution of 68Ga-DOTA-TATE in pediatric patients

OBJECTIVE

Somatostatin receptors (SSTRs) are G protein-coupled transmembrane receptors that serve as a specific molecular target for a number of radiopharmaceuticals utilized for the imaging of neuroendocrine tumors (NETs). 68Ga-DOTA-TATE is a somatostatin analog that demonstrates a high affinity for SSTR2. Pediatric malignancies, such as neuroblastoma, pheochromocytoma, and paraganglioma, have been shown to express SSTR2, and 68Ga-DOTA-TATE is currently being used to evaluate these pediatric neoplasms. We aimed to analyze the distribution pattern of 68Ga-DOTA-TATE based on age and location in pediatric patients.

METHODS

We retrospectively analyzed 247 consecutive 68Ga-DOTA-TATE whole-body PET/CT scans performed in our department from May 2015 to April 2024 in pediatric patients with known or suspected neuroblastoma, neuroendocrine malignancy, pheochromocytoma, and paraganglioma. 93 subjects were included in this study who were disease-free at the time of imaging and had no tracer-avid lesion on 68Ga-DOTA-TATE PET/CT. The patients were divided into four groups according to age: infant (0-2 years), pre-school (3-6 years), school (7-12 years), and adolescent (13-18 years). A comparison of the SUV values of each organ across age groups was performed.

RESULTS

The highest levels of physiological uptake were observed in the spleen across all age groups, except for infants, who demonstrated the highest SUV values in the kidneys. 68Ga-DOTA-TATE uptake in the parotid glands, submandibular glands, thyroid gland, thymus, liver, spleen, adrenal glands, stomach, intestines, uterus, prostate, and testes demonstrated a statistically significant increase in the adolescent age group. In contrast to all internal organs, the lowest SUV max values were observed for all growth plates within the adolescent age group.

CONCLUSION

This study presents the bio-distribution pattern of 68Ga-DOTA-TATE in pediatric patients, according to age and location. The ranges of the SUVmax and SUVmean values of 68Ga-DOTA-TATE obtained in the various organs are of paramount importance for accurately diagnosing malignancy in 68Ga-DOTA-TATE PET/CT studies.

Case Series of Patients With FGFR1-Related Pheochromocytoma and Paraganglioma With a Focus on Biochemical, Imaging Signatures and Treatment Options

Pheochromocytoma and paraganglioma (together PPGL) are tumours with a high degree of heritability. Genetic landscape is divided into three clusters, cluster 1 (Krebs/pseudohypoxia signalling pathway), cluster 2 (kinase signalling pathway) and cluster 3 (Wnt signalling pathway). With increasing knowledge in the field of genetics, cluster-specific tumour characteristics, biochemical phenotype and imaging signatures are established in commonly found genes. The association of FGFR1 pathogenic mutations with PPGL have been recently described although its features are not yet well established. Here, we present four patients with PPGL who were found to have somatic FGFR1 pathogenic mutations. We discuss their clinical presentations, biochemical phenotypes, imaging signatures and treatment options that will be relevant for practicing physicians in managing these patients effectively.

Imaging of Pheochromocytomas and Paragangliomas

Pheochromocytomas/paragangliomas are unique in their highly variable molecular landscape driven by genetic alterations, either germline or somatic. These mutations translate into different clusters with distinct tumor locations, biochemical/metabolomic features, tumor cell characteristics (eg, receptors, transporters), and disease course. Such tumor heterogeneity calls for different imaging strategies in order to provide proper diagnosis and follow-up. This also warrants selection of the most appropriate and locally available imaging modalities tailored to an individual patient based on consideration of many relevant factors including age, (anticipated) tumor location(s), size, and multifocality, underlying genotype, biochemical phenotype, chance of metastases, as well as the patient's personal preference and treatment goals. Anatomical imaging using computed tomography and magnetic resonance imaging and functional imaging using positron emission tomography and single photon emission computed tomography are currently a cornerstone in the evaluation of patients with pheochromocytomas/paragangliomas. In modern nuclear medicine practice, a multitude of radionuclides with relevance to diagnostic work-up and treatment planning (theranostics) is available, including radiolabeled metaiodobenzylguanidine, fluorodeoxyglucose, fluorodihydroxyphenylalanine, and somatostatin analogues. This review amalgamates up-to-date imaging guidelines, expert opinions, and recent discoveries. Based on the rich toolbox for anatomical and functional imaging that is currently available, we aim to define a customized approach in patients with (suspected) pheochromocytomas/paragangliomas from a practical clinical perspective. We provide imaging algorithms for different starting points for initial diagnostic work-up and course of the disease, including adrenal incidentaloma, established biochemical diagnosis, postsurgical follow-up, tumor screening in pathogenic variant carriers, staging and restaging of metastatic disease, theranostics, and response monitoring.

Surgical strategies of complicated pheochromocytomas/paragangliomas and literature review

Pheochromocytomas (PCC)/paragangliomas (PGL) are catecholamine (CA) -secreting neuroendocrine tumors, which are known as PPGL due to their histological and pathophysiological similarities. In addition to the typical triad of paroxysmal headache, palpitation, and sweating, PPGL may also be accompanied by symptoms and signs involving multiple organs and systems such as the cardiovascular system, digestive system, endocrine system, and nervous system. Currently, surgical resection is the first choice for PPGL. Safe and effective surgical management of complicated PPGL is the goal of clinical work. In this paper, we discuss this hot issue based on complicated PPGL cases, aiming to share our experience of the surgical management strategy of PPGL.

[Pheochromocytoma and paraganglioma during childhood and adolescence]

BACKGROUND

Pheochromocytoma and paraganglioma belong to the group of rare catecholamine-producing tumours during childhood and adolescence. They occur most frequently in patients with tumour predisposition syndromes. Imaging is essential to assess tumour stage and to plan therapy initiation.

OBJECTIVE

The aim of this review is a summary of the most important characteristics of the aforementioned tumour entities with a special focus on imaging. In particular, magnetic resonance imaging (MRI) as well as nuclear medicine techniques are presented.

MATERIALS AND METHODS

Diagnostic methods in patients with pheochromocytoma and paraganglioma are presented based on the literature and own case reports.

RESULTS

The radiologic modality of choice for the staging of catecholamine-producing tumours during childhood and adolescence is MRI, due to the lack of ionizing radiation and high soft tissue contrast. In addition, 123-I-meta-iodo-benzyl-guanidine (MIBG) scintigraphy and positron emission tomography/computer tomography (PET/CT) are performed. Whole-body MRI is particularly important as a screening tool in patients with a tumour predisposition syndrome.

CONCLUSIONS

Radiologic imaging and nuclear medicine techniques are important for the assessment of disease stage and therapy planning in patients with catecholamine-producing tumours. Detection of metastatic disease is essential, as there are no known histopathologic markers, which can predict the metastatic potential of the tumours.