Performance of 68Ga-DOTA–Conjugated Somatostatin Receptor–Targeting Peptide PET in Detection of Pheochromocytoma and Paraganglioma: A Systematic Review and Metaanalysis

Subclinical phaeochromocytoma: a diagnostic and management challenge

There is a paradigm shift in the detection of phaeochromocytomas with more being identified as adrenal 'incidentalomas'. While majority of these individuals are asymptomatic, they are nevertheless at risk of subtle cardiovascular dysfunction and phaeochromocytoma crises. Therefore, early resection of phaeochromocytomas, even if subclinical, is recommended. However, the perioperative management can be challenging as the normotension can limit the initiation and titration of alpha-blockade. We present a man in his 60s with a subclinical phaeochromocytoma, discuss the evaluation of an incidentally discovered adrenal nodule, as well as the practical considerations in the perioperative management.

Integrated PET/MRI With 68Ga-DOTATATE and 18F-FDG in Pheochromocytomas and Paragangliomas: An Initial Study

PURPOSE

Pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors with metastatic potential. Both 68Ga-DOTATATE and 18F-FDG PET/CT scans have been demonstrated to have important roles in imaging PPGLs, but less is known about the performance of PET/MRI for PPGLs. The study is aimed to investigate whether diffusion-weighted imaging-MRI (DWI-MRI) has an added value to PET imaging in the identification of PPGL lesions by means of integrated PET/MRI.

METHODS

Eleven patients who underwent both 18F-FDG and 68Ga-DOTATATE PET/MRI within 2 weeks were retrospectively included in the study. A total of 56 PPGL lesions were analyzed, and lesion-based detection rates of 68Ga-DOTATATE PET, 18F-FDG PET, DWI-MRI, and PET/MRI were calculated and compared, respectively.

RESULTS

68Ga-DOTATATE PET was superior to 18F-FDG PET and DWI-MRI in imaging PPGLs with a lesion-based detection rate of 96.4% (54/56) (95% confidence interval [CI], 87.7%-99.6%), 85.7% (48/56) (95% CI, 76.3%-95.2%), and 89.3% (50/56) (95% CI, 80.9%-97.6%), respectively. PET/MRI with DWI could improve the detection rate of 68Ga-DOTATATE and 18F-FDG PET alone up to 100% in metastatic PPGLs. Lesions of PPGL demonstrated markedly higher tracer uptake in 68Ga-DOTATATE PET than in 18F-FDG PET (P = 0.009 for primary lesion, P = 0.033 for metastases).

CONCLUSIONS

68Ga-DOTATATE PET showed a higher detection rate than 18F-FDG for PPGLs. In integrated PET/MRI, MRI had an added value to 18F-FDG PET but not much to 68Ga-DOTATATAE PET in identifying PPGL lesions.

Overexpression of miR-375 and L-type Amino Acid Transporter 1 in Pheochromocytoma and Their Molecular and Functional Implications

Pheochromocytoma (Pheo) is a tumor derived from chromaffin cells. It can be studied using 18F-dihydroxyphenylalanine (DOPA)—positron emission tomography (PET) due to its overexpression of L-type amino acid transporters (LAT1 and LAT2). The oncogenic pathways involved are still poorly understood. This study examined the relationship between ¹⁸F-DOPA-PET uptake and LAT1 expression, and we explored the role of miR-375 and putative target genes. A consecutive series of 58 Pheo patients were retrospectively analyzed, performing ¹⁸F-DOPA-PET in 32/58 patients. Real-time quantitative PCR was used to assess the expression of LAT1, LAT2, phenylethanolamine N-methyltransferase (PNMT), miR-375, and the major components of the Hippo and Wingless/Integrated pathways. Principal germline mutations associated with hereditary Pheo were also studied. Pheo tissues had significantly higher LAT1, LAT2, and PNMT mRNA levels than normal adrenal tissues. MiR-375 was strongly overexpressed. Yes-associated protein 1 and tankyrase 1 were upregulated, while beta-catenin, axin2, monocarboxylate transporter 8, and Frizzled 8 were downregulated. A positive relationship was found between ¹⁸F-DOPA-PET SUV mean and LAT1 gene expression and for 24 h-urinary norepinephrine and LAT1. This is the first experimental evidence of ¹⁸F-DOPA uptake correlating with LAT1 overexpression. We also demonstrated miR-375 overexpression and downregulated (Wnt) signaling and identified the Hippo pathway as a new potentially oncogenic feature of Pheo.

Radiolabeled Somatostatin Analogues for Diagnosis and Treatment of Neuroendocrine Tumors

Neuroendocrine neoplasms (NENs) are rare and heterogeneous tumors that require multidisciplinary discussion for optimal care. The theranostic approach (DOTA peptides labelled with 68Ga for diagnosis and with 90Y or 177Lu for therapy) plays a crucial role in the management of NENs to assess disease extension and as a criteria for peptide receptor radionuclide therapy (PRRT) eligibility based on somatostatin receptor (SSTR) expression. On the diagnostic side, [68Ga]Ga-DOTA peptides PET/CT (SSTR PET/CT) is the gold standard for imaging well-differentiated SSTR-expressing neuroendocrine tumors (NETs). [18F]FDG PET/CT is useful in higher grade NENs (NET G2 with Ki-67 > 10% and NET G3; NEC) for more accurate disease characterization and prognostication. Promising emerging radiopharmaceuticals include somatostatin analogues labelled with 18F (to overcome the limits imposed by 68Ga), and SSTR antagonists (for both diagnosis and therapy). On the therapeutic side, the evidence gathered over the past two decades indicates that PRRT is to be considered as an effective and safe treatment option for SSTR-expressing NETs, and is currently included in the therapeutic algorithms of the main scientific societies. The positioning of PRRT in the treatment sequence, as well as treatment personalization (e.g., tailored dosimetry, re-treatment, selection criteria, and combination with other alternative treatment options), is warranted in order to improve its efficacy while reducing toxicity. Although very preliminary (being mostly hampered by lack of methodological standardization, especially regarding feature selection/extraction) and often including small patient cohorts, radiomic studies in NETs are also presented. To date, the implementation of radiomics in clinical practice is still unclear. The purpose of this review is to offer an overview of radiolabeled SSTR analogues for theranostic use in NENs.

Genetics of Pheochromocytomas and Paragangliomas Determine the Therapeutical Approach

Pheochromocytomas and paragangliomas are the most heritable endocrine tumors. In addition to the inherited mutation other driver mutations have also been identified in tumor tissues. All these genetic alterations are clustered in distinct groups which determine the pathomechanisms. Most of these tumors are benign and their surgical removal will resolve patient management. However, 5–15% of them are malignant and therapeutical possibilities for them are limited. This review provides a brief insight about the tumorigenesis associated with pheochromocytomas/paragangliomas in order to present them as potential therapeutical targets.

Adrenal Mass Characterization in the Era of Quantitative Imaging: State of the Art

Simple Summary

Non-invasive characterization of adrenal lesions requires a rigorous approach. Although CT is the cornerstone of adrenal lesion characterization, a multimodality multiparametric imaging approach helps improve confidence in adrenal lesion characterization.

Abstract

Detection and characterization of adrenal lesions have evolved during the past two decades. Although the role of imaging in adrenal lesions associated with hormonal secretion is usually straightforward, characterization of non-functioning adrenal lesions may be challenging to confidently identify those that need to be resected. Although many adrenal lesions can be readily diagnosed when they display typical imaging features, the diagnosis may be challenging for atypical lesions. Computed tomography (CT) remains the cornerstone of adrenal imaging, but other morphological or functional modalities can be used in combination to reach a diagnosis and avoid useless biopsy or surgery. Early- and delayed-phase contrast-enhanced CT images are essential for diagnosing lipid-poor adenoma. Ongoing studies are evaluating the capabilities of dual-energy CT to provide valid virtual non-contrast attenuation and iodine density measurements from contrast-enhanced examinations. Adrenal lesions with attenuation values between 10 and 30 Hounsfield units (HU) on unenhanced CT can be characterized by MRI when iodinated contrast material injection cannot be performed. ¹⁸F-FDG PET/CT helps differentiate between atypical benign and malignant adrenal lesions, with the adrenal-to-liver maximum standardized uptake value ratio being the most discriminative variable. Recent studies evaluating the capabilities of radiomics and artificial intelligence have shown encouraging results.

Site-based performance of 131I-MIBG imaging and 99mTc-HYNIC-TOC scintigraphy in the detection of nonmetastatic extra-adrenal paraganglioma

OBJECTIVES

This study aimed to evaluate the performance of 131I-metaiodobenzylguanidine (MIBG) imaging to detect nonmetastatic extra-adrenal paragangliomas at their respective sites (abdominal vs. thoracic vs. head and neck vs. urinary bladder), and compare it with that of 99mTc-hydrazinonicotinyl-tyr3-octreotide (HYNIC-TOC) scintigraphy.

METHODS

We retrospectively analyzed 235 patients with nonmetastatic extra-adrenal paragangliomas who underwent preoperative 131I-MIBG imaging or 99mTc-HYNIC-TOC scintigraphy. Of all 235 patients, 145 patients underwent both imaging procedures, 16 patients 131I-MIBG imaging only and 74 patients 99mTc-HYNIC-TOC scintigraphy only.

RESULTS

The overall sensitivity of 131I-MIBG and 99mTc-HYNIC-TOC imaging to detect extra-adrenal paragangliomas regardless of tumor sites was 75.8% (122/161) and 67.6% (148/219), respectively (P = 0.082). However, when stratified by tumor sites, 131I-MIBG imaging showed a significant improvement in the detection of extra-adrenal abdominal paragangliomas with a sensitivity of 90.3% (103/114), which was significantly higher than that of 99mTc-HYNIC-TOC scintigraphy (67.6% (96/142); P = 0.000). In addition, the intensity of tracer uptake in the extra-adrenal abdominal paragangliomas with 131I-MIBG imaging was evidently higher than with 99mTc-HYNIC-TOC scintigraphy. The sensitivity of 131I-MIBG imaging and 99mTc-HYNIC-TOC scintigraphy to detect urinary bladder, head and neck, and thoracic paragangliomas were 18.7 vs. 18.5% (P = 1.000); 17.4% vs. 84.6% (P = 0.000) and 60% vs. 94.4% (P = 0.030), respectively.

CONCLUSIONS

131I-MIBG imaging could become the first-line investigation modality in patients with extra-adrenal abdominal paragangliomas. However, 99mTc-HYNIC-TOC scintigraphy has high sensitivity and is superior to 131I-MIBG imaging for detecting head & neck and thoracic paraganglioma. Both 131I-MIBG imaging and 99mTc-HYNIC-TOC scintigraphy have poor performance for detecting urinary bladder paragangliomas.

Pediatric Metastatic Pheochromocytoma and Paraganglioma: Clinical Presentation and Diagnosis, Genetics, and Therapeutic Approaches

Although pediatric pheochromocytomas and paragangliomas (PPGLs) are rare, they have important differences compared to those in adults. Unfortunately, without timely diagnosis and management, these tumors have a potentially devastating impact on pediatric patients. Pediatric PPGLs are more often extra-adrenal, multifocal/metastatic, and recurrent, likely due to these tumors being more commonly due to a genetic predisposition than in adults. This genetic risk results in disease manifestations at an earlier age giving these tumors time to advance before detection. In spite of these problematic features, advances in the molecular and biochemical characterization of PPGLs have heralded an age of increasingly personalized medicine. An understanding of the genetic basis for an individual patient's tumor provides insight into its natural history and can guide clinicians in management of this challenging disease. In pediatric PPGLs, mutations in genes related to pseudohypoxia are most commonly seen, including the von Hippel-Lindau gene (VHL) and succinate dehydrogenase subunit (SDHx) genes, with the highest risk for metastatic disease associated with variants in SDHB and SDHA. Such pathogenic variants are associated with a noradrenergic biochemical phenotype with resultant sustained catecholamine release and therefore persistent symptoms. This is in contrast to paroxysmal symptoms (e.g., episodic hypertension, palpitations, and diaphoresis/flushing) as seen in the adrenergic, or epinephrine-predominant, biochemical phenotype (due to episodic catecholamine release) that is commonly observed in adults. Additionally, PPGLs in children more often present with signs and symptoms of catecholamine excess. Therefore, children, adolescents, and young adults present differently from older adults (e.g., the prototypical presentation of palpitations, perspiration, and pounding headaches in the setting of an isolated adrenal mass). These presentations are a direct result of genetic determinants and highlight the need for pediatricians to recognize these differences in order to expedite appropriate evaluations, including genetic testing. Identification and familiarity with causative genes inform surveillance and treatment strategies to improve outcomes in pediatric patients with PPGL.

Radiotheranostics - Precision Medicine in Nuclear Medicine and Molecular Imaging

'See what you treat and treat what you see, at a molecular level', could be the motto of theranostics. The concept implies diagnosis (imaging) and treatment of cells (usually cancer) using the same molecule, thus guaranteeing a targeted cytotoxic approach of the imaged tumor cells while sparing healthy tissues. As the brilliant late Sam Gambhir would say, the imaging agent acts like a 'molecular spy' and reveals where the tumoral cells are located and the extent of disease burden (diagnosis). For treatment, the same 'molecular spy' docks to the same tumor cells, this time delivering cytotoxic doses of radiation (treatment). This duality represents the concept of a 'theranostic pair', which follows the scope and fundamental principles of targeted precision and personalized medicine. Although the term theranostic was noted in medical literature in the early 2000s, the principle is not at all new to nuclear medicine. The first example of theranostic dates back to 1941 when Dr. Saul Hertz first applied radioiodine for radionuclide treatment of thyroid cells in patients with hyperthyroidism. Ever since, theranostics has been an integral element of nuclear medicine and molecular imaging. The more we understand tumor biology and molecular pathology of carcinogenesis, including specific mutations and receptor expression profiles, the more specific these 'molecular spies' can be developed for diagnostic molecular imaging and subsequent radionuclide targeted therapy (radiotheranostics). The appropriate selection of the diagnostic and therapeutic radionuclide for the 'theranostic pair' is critical and takes into account not only the type of cytotoxic radiation emission, but also the linear energy transfer (LET), and the physical half-lives. Advances in radiochemistry and radiopharmacy with new radiolabeling techniques and chelators are revolutionizing the field. The landscape of cytotoxic systemic radionuclide treatments has dramatically expanded through the past decades thanks to all these advancements. This article discusses present and promising future theranostic applications for various types of diseases such as thyroid disorders, neuroendocrine tumors (NET), pediatric malignancies, and prostate cancer (PC), and provides an outlook for future perspectives.

Robotic excision of interaortocaval paraganglioma: a case report with the literature review

Background

Paragangliomas are rare neuroendocrine tumors of extra adrenal origin. The symptomatic paragangliomas require multimodal treatment approach.

Case Presentation

We report a case of 34-year-old female who presented with complains of headache and blurring of vision. Examination revealed Hypertensive crisis with grade 3 retinopathy. The patient was diagnosed as a case of extra-adrenal paraganglioma during evaluation for secondary hypertension. Magnetic Resonance Imaging of the abdomen revealed 23*28*28 mm mass lesion in the inter-aortocaval region at the level of L3–L4. The patient was started on medical management for hypertension and was managed safely with robot-assisted surgery, owing to enhanced visualization of feeding vessels and avoidance of excessive manipulation of tumor.

Conclusions

Our case report emphasizes on the robot assisted surgical technique for the removal of tumor in a vulnerable anatomical position and presents a review of the literature.

Unclear retroperitoneal tumors, an interdisciplinary challenge - A case report and review of the literature

INTRODUCTION AND IMPORTANCE

Unclear retroperitoneal tumors impose major challenges for clinicians. Tumors can originate primarily from retroperitoneal tissue or secondarily invade into the retroperitoneum. While benign lesions also occur, malignant tumors are far more common. Clinical presentation depends on replacement or invasion of other organs and is therefore highly variable. The heterogeneous tumor composition makes a definitive preoperative diagnosis difficult. Surgical resection is the gold standard for treatment but often proves challenging due to frequent involvement of large retroperitoneal vessels.

CASE PRESENTATION

We present the case of a 70-year old woman diagnosed with a large, unclear retroperitoneal tumor. Initial clinical symptoms were increasing dyspnea and dysphagia in our clinic. Gastroenterologic and cardiologic workup was unremarkable. Computed Tomography (CT) revealed a large retroperitoneal mass in the right upper abdomen with severe displacement of the inferior vena cava and renal veins. The patient was scheduled for primary tumor resection. The procedure was challenging due to the vessel involvement and large blood pressure alterations during tumor mobilization. The post-op pathologic workup then revealed the rare finding of a completely resected paraganglioma. The post-surgical course was uneventful. One year after diagnosis, the patient is relapse-free.

CLINICAL DISCUSSION

Among retroperitoneal tumors, paragangliomas and pheochromocytomas are rare tumor entities. Asymptomatic, sporadic disease is hard to identify preoperatively and can cause unexpected complications in the OR. An experienced team is crucial in achieving best short- and long-term outcomes.

CONCLUSION

This case impressively shows the challenges of retroperitoneal tumors and the importance of interdisciplinary work in these cases.

KSNM60 in Clinical Nuclear Oncology

Since the foundation of the Korean Society of Nuclear Medicine in 1961, clinical nuclear oncology has been a major part of clinical nuclear medicine in Korea. There are several important events for the development of clinical nuclear oncology in Korea. First, a scintillating type gamma camera was adopted in 1969, which enabled to perform modern oncological gamma imaging. Second, Tc-99 m generator was imported to Korea since 1979, which promoted the wide clinical use of gamma camera imaging by using various kinds of Tc-99 m labeled radiopharmaceuticals. Third, a gamma camera with single photon emission tomography (SPECT) capability was first installed in 1980, which has been used for various kinds of tumor SPECT imaging. Fourth, in 1994, clinical positron emission tomography (PET) scanner and cyclotron with a production of F-18 fluorodeoxyglucose were first installed in Korea. Fifth, Korean Board of Nuclear Medicine was established in 1995, which contributed in the education and manpower training of dedicated nuclear medicine physicians in Korea. Finally, an integrated PET/CT scanner was first installed in 2002. Since that, PET/CT imaging has been a major imaging tool in clinical nuclear oncology in Korea. In this review, a brief history of clinical nuclear oncology in Korea is described.

PET with Different Radiopharmaceuticals in Neuroendocrine Neoplasms: An Umbrella Review of Published Meta-Analyses

Simple Summary

Functional imaging methods and, in particular, positron emission tomography (PET) using several radiopharmaceuticals may play a pivotal role in patients with neuroendocrine neoplasms including neuroendocrine tumors (NETs) located in different sites, paraganglioma (PGL) and neuroblastoma (NB), recurrent medullary thyroid carcinoma (rMTC) and aggressive neuroendocrine neoplasms. Several radiopharmaceuticals can be used in this setting such as Gallium-68 somatostatin analogues (⁶⁸Ga-SSA), Fluorine-18 fluorodihydroxyphenylalanine (¹⁸F-FDOPA), Gallium-68 exendin-4 (⁶⁸Ga-exendin-4), Fluorine-18 fluorodeoxyglucose (¹⁸F-FDG). This umbrella review provides an evidence-based summary about meta-analyses on diagnostic performance, prognostic value, clinical impact and safety of PET with different radiopharmaceuticals in patients with neuroendocrine neoplasms. Overall, evidence-based data support the use of PET with different radiopharmaceuticals in patients with neuroendocrine neoplasms but with specific indications for each radiopharmaceutical.

Abstract

Background: Several meta-analyses have reported quantitative data about the diagnostic performance, the prognostic value, the impact on management and the safety of positron emission tomography (PET) including related hybrid modalities (PET/CT or PET/MRI) using different radiopharmaceuticals in patients with neuroendocrine neoplasms. We performed an umbrella review of published meta-analyses to provide an evidence-based summary. Methods: A comprehensive literature search of meta-analyses listed in PubMed/MEDLINE and Cochrane Library databases was carried out (last search date: 30 June 2021). Results: Thirty-four published meta-analyses were selected and summarized. About the diagnostic performance: ⁶⁸Ga-SSA PET yields high diagnostic performance in patients with NETs and PGL; ¹⁸F-FDOPA PET yields good diagnostic performance in patients with intestinal NETs, PGL, NB, being the best available PET method in detecting rMTC; ⁶⁸Ga-exendin-4 PET has good diagnostic accuracy in detecting insulinomas; ¹⁸F-FDG PET has good diagnostic performance in detecting aggressive neuroendocrine neoplasms. About the prognostic value: ⁶⁸Ga-SSA PET has a recognized prognostic value in well-differentiated NETs, whereas ¹⁸F-FDG PET has a recognized prognostic value in aggressive neuroendocrine neoplasms. A significant clinical impact of ⁶⁸Ga-SSA PET and related hybrid modalities in patients with NETs was demonstrated. There are no major toxicities or safety issues related to the use of PET radiopharmaceuticals in patients with neuroendocrine neoplasms. Conclusions: Evidence-based data support the use of PET with different radiopharmaceuticals in patients with neuroendocrine neoplasms with specific indications for each radiopharmaceutical.

Special situations in pheochromocytomas and paragangliomas: pregnancy, metastatic disease, and cyanotic congenital heart diseases

The aim of our study was to describe the epidemiology, diagnosis, and treatment of the most complex pheochromocytoma and paraganglioma (PGL) cases, including pheochromocytoma/PGL during pregnancy, in cyanotic congenital heart diseases (CCHDs), and metastatic pheochromocytoma. The English and Spanish literature was thoroughly evaluated searching for articles reporting clinical studies, case reports, or reviews of pheochromocytoma/PGL in pregnancy and in CCHD and metastatic pheochromocytoma/PGL. Particular settings in the diagnosis and management of pheochromocytoma and PGLs remain challenging. Those special situations include the diagnosis during pregnancy or in the context of CCHD since the typical clinical features of pheochromocytoma may be confounded with preeclampsia during pregnancy and with the complications commonly observed in CCHD. In addition, although some clinical and genetic features have been associated with higher risk of metastatic pheochromocytoma, the detection and prediction of the development of metastatic disease involve another complex situation that may require special hormonal determinations as plasmatic 3-methoxytyramine and nuclear medicine studies including ¹⁸FDG PET-CT or ¹⁸F-FDOPA PET-CT, among others. Furthermore, the selection of the most appropriate treatment in these situations, as well as the moment to carry it out, requires special care as limited evidence is available. This article reviews the epidemiology, diagnosis, and treatment of the pheochromocytoma/PGL during pregnancy, metastatic pheochromocytoma/PGL, and pheochromocytoma/PGL in CCHD. The diagnosis, and especially the treatment, of metastatic pheochromocytomas and pheochromocytoma/PGL during pregnancy and in CCHD is challenging. Thus, these cases should be management in reference centres by multidisciplinary teams specialized in the pheochromocytoma/PGL treatment.

Diagnostic performance of [124I]m-iodobenzylguanidine PET/CT in patients with pheochromocytoma

^123/131I-MIBG scintigraphy has shown a high specificity for imaging pheochromocytoma and paraganglioma however with low sensitivity due to low spatial resolution. ¹²⁴I-MIBG PET may overcome this limitation to improve the staging of patients with (suspected) pheochromocytoma. Methods: We analyzed the sensitivity, specificity, positive and negative predictive values (PPV, NPV) of ¹²⁴I-MIBG PET in 43 consecutive patients with suspected (recurrence of) pheochromocytoma using histopathological (n = 25) and clinical validation (n = 18) as standard of truth. Furthermore, we compared ¹²⁴I-MIBG PET versus contrast enhanced CT (CE-CT) per-patient and per-lesion detection rate of ¹²⁴I-MIBG PET in 13 additional patients with known metastatic malignant pheochromocytoma (MMP). Results: ¹²⁴I-MIBG PET/CT was positive in 19/43 (44%) patients with suspected pheochromocytoma. Presence of pheochromocytoma was confirmed in 22/43 (51%). ¹²⁴I-MIBG PET/CT sensitivity, specificity, PPV, NPV were 86%, 100%, 100%, 88%, respectively. ¹²⁴I-MIBG PET was positive in 11/13 (85%) MMP patients. Combined ¹²⁴I-MIBG PET and CE-CT detected 173 lesions, of which 166 (96%) and 118 (68%) were visible on ¹²⁴I-MIBG PET and CE-CT, respectively. Discussion: ¹²⁴I-MIBG PET detects pheochromocytoma with high accuracy at initial staging and high detection rate at re-staging. Superior diagnostic performance aids guidance of surgical and medical management including personalized ¹³¹I-MIBG therapy.

Insights into Mechanisms of Pheochromocytomas and Paragangliomas Driven by Known or New Genetic Drivers

Simple Summary

Pheochromocytomas and paragangliomas are rare neuroendocrine tumors that are often hereditary. Although research has advanced considerably, significant gaps still persist in understanding risk factors, predicting metastatic potential and treating aggressive tumors. The study of rare mutations can provide new insights into how pheochromocytomas and paragangliomas develop. In this review, we provide examples of such rare events and how they can inform our understanding of the spectrum of mutations that can lead to these tumors and improve our ability to provide a genetic diagnosis.

Abstract

Pheochromocytomas and paragangliomas are rare tumors of neural crest origin. Their remarkable genetic diversity and high heritability have enabled discoveries of bona fide cancer driver genes with an impact on diagnosis and clinical management and have consistently shed light on new paradigms in cancer. In this review, we explore unique mechanisms of pheochromocytoma and paraganglioma initiation and management by drawing from recent examples involving rare mutations of hypoxia-related genes VHL, EPAS1 and SDHB, and of a poorly known susceptibility gene, TMEM127. These models expand our ability to predict variant pathogenicity, inform new functional domains, recognize environmental-gene connections, and highlight persistent therapeutic challenges for tumors with aggressive behavior.

Two Birds with One Stone: Skull Base Meningioma and Jugulotympanic Paragangliomas with Somatostatin Receptor Positron Emission Tomography

We describe the case of a 74-year-old female patient previously treated with radiation therapy for a meningioma of the skull base and with surgery for a right tympanic paraganglioma. After the morphological progression of the meningioma demonstrated by magnetic resonance imaging (MRI), the patient underwent somatostatin receptor positron emission tomography/computed tomography (SR-PET/CT) with Gallium-68 DOTATATE for restaging. This examination showed increased somatostatin receptor expression by the meningioma and confirmed its extension as already assessed by MRI (endocranial extension, skull base involvement and invasion of the right orbit). Furthermore, SR-PET/CT detected two small right jugulotympanic pararagangliomas with high somatostatin receptor expression. Lastly, SR-PET/CT demonstrated that this patient would be an ideal candidate for peptide receptor radionuclide therapy (PRRT) that can be used for the treatment of progressive/treatment-refractory meningiomas and relapsed paragangliomas with high somatostatin receptors expression, both conditions coexisting in this case.

Genetic stratification of inherited and sporadic phaeochromocytoma and paraganglioma: implications for precision medicine

Over the past two decades advances in genomic technologies have transformed knowledge of the genetic basis of phaeochromocytoma and paraganglioma (PPGL). Though traditional teaching suggested that inherited cases accounted for only 10% of all phaeochromocytoma diagnosis, current estimates are at least three times this proportion. Inherited PPGL is a highly genetically heterogeneous disorder but the most frequently results from inactivating variants in genes encoding subunits of succinate dehydrogenase. Expanding knowledge of the genetics of PPGL has been translated into clinical practice by the provision of widespread testing for inherited PPGL. In this review, we explore how the molecular stratification of PPGL is being utilized to enable more personalized strategies for investigation, surveillance and management of affected individuals and their families. Translating recent genetic research advances into clinical service can not only bring benefits through more accurate diagnosis and risk prediction but also challenges when there is a suboptimal evidence base for the clinical consequences or significance of rare genotypes. In such cases, clinical, biochemical, pathological and functional imaging assessments can all contribute to more accurate interpretation and clinical management.

Sporadic Primary Pheochromocytoma: A Prospective Intra-Individual Comparison of Six Imaging Tests (CT, MRI, and PET/CT Using 68Ga-DOTATATE, FDG, 18F-FDOPA, and 18F-FDA)

Background: Recent professional society guidelines for radionuclide imaging of sporadic pheochromocytoma (PHEO) recommend 18F-FDOPA as the radiotracer of choice, deeming 68Ga-DOTATATE and FDG to be secondand third-line agents, respectively. An additional agent, 18F-FDA, remains experimental for PHEO detection. A paucity of research has performed head-to-head comparison among these agents. Purpose: To perform an intra-individual comparison of 68Ga-DOTATATE PET/CT, FDG PET/CT, 18F-FDOPA PET/CT, 18F-FDA PET/CT, CT, and MRI in visualization of sporadic primary PHEO. Methods: This prospective study enrolled patients referred with clinical suspicion for sporadic PHEO. Patients were scheduled for 68Ga-DOTATATE PET/CT, FDG PET/CT, 18F-FDOPA PET/CT, 18F-FDA PET/CT, whole-body staging CT (portal venous phase), and MRI, within a 3-month period. PET/CT examinations were reviewed by two nuclear medicine physicians, and CT and MRI were reviewed by two radiologists; differences were resolved by consensus. Readers scored lesions in terms of confidence in diagnosis of PHEO (1-5 scale; 4-5 considered positive for PHEO). Lesion-to-liver SUVmax was computed using both readers' measurements. Interreader agreement was assessed, using intraclass correlation coefficients (ICCs) for SUVmax. Analysis included only patients with histologically- confirmed PHEO on resection. Results: The analysis included 14 patients (8 women, 6 men; mean age, 52.4±16.8 years) with PHEO. Both 68Ga-DOTATATE PET/CT and FDG PET/CT were completed in 14/14 patients, 18F-FDOPA PET/CT in 11/14, 18F-FDA PET/CT in 7/14, CT in 12/14, and MRI in 12/14. Mean conspicuity score for PHEO was 5.0±0.0 for 18F-FDOPA PET/ CT, 4.7±0.5 for MRI, 4.6±0.8 for 18F-FDA PET/CT, 4.4±1.0 for 68Ga-DOTATATE PET/CT, 4.3±1.0 for CT, and 4.1±1.5 for FDG PET/CT. The positivity rate for PHEO was 100.0% (11/11) for 18F-FDOPA PET/CT, 100.0% (12/12) for MRI, 85.7% (6/7) for 18F-FDA PET/CT, 78.6% (11/14) for FDG PET/CT, 78.6% (11/14) for 68Ga-DOTATATE, and 66.7% (8/12) for CT. Lesion-to-liver SUVmax was 10.5 for 18F-FDOPA versus 3.0-4.2 for the other tracers. Interreader agreement across modalities ranged from 85.7-100.0% for lesion positivity and from ICC=0.55-1.00 for SUVmax measurements. Conclusion: Findings from this small intra-individual comparative study support 18F-FDOPA PET/CT as a preferred firstline imaging modality in evaluation of sporadic PHEO. Clinical Impact: This study provides data supporting current guidelines for imaging evaluation of suspected PHEO.

Imaging of Pheochromocytoma and Paraganglioma

Imaging plays a critical role in the management of pheochromocytomas and paragangliomas and often guides treatment. The discovery of susceptibility genes associated with these tumors has led to better understanding of clinical and imaging phenotypes. Functional imaging is of prime importance because of its sensitivity and specificity in subtypes of pheochromocytoma and paraganglioma. Several radiopharmaceuticals have been developed to target specific receptors and metabolic processes seen in pheochromocytomas and paragangliomas, including 131I/123I-metaiodobenzylguanidine, 6-18F-fluoro-l-3,4-dihydroxyphenylalanine, 18F-FDG, and 68Ga-DOTA-somatostatin analogs. Two of these have consequently been adapted for therapy. This educational review focuses on the current imaging approaches used in pheochromocytomas and paragangliomas, which vary among clinical and genotypic presentations.

A Clinical Challenge: Endocrine and Imaging Investigations of Adrenal Masses

Incidentalomas are reported in 3%-4% of patients who undergo abdominal anatomic imaging, making adrenal mass evaluation a common occurrence. An adrenal mass can be caused by a variety of pathologies, such as benign cortical and medullary tumors, malignant tumors (primary or secondary), cysts, hyperplasia, hemorrhage, or more rarely infection/inflammation processes. Functioning tumors usually have increased hormonal production but they are less common. Regardless of their functional status, some tumors have the potential to behave aggressively. Anatomic and functional imaging together with biologic evaluation play a vital role in adrenal pathology subtyping. Most patients are initially evaluated by CT or MRI, which allows for tumor characterization (to a certain extent) and can rule out malignant behavior based on the absence of tumor growth during longitudinal follow-up. In the remaining patients for whom CT or MRI fail to characterize the pathogenesis of adrenal tumors, the use of specialized molecular imaging techniques should be performed after hormonal screening. This review emphasizes well-established and emerging nuclear medicine imaging modalities and describes their use across various clinical scenarios.

Squamous Cell Carcinoma Mimicking Neck Paraganglioma on 68Ga-DOTATATE PET/CT

ABSTRACT

Somatostatin receptor (SSTR) imaging with 68Ga-labeled somatostatin analogs has been used for many tumors with high SSTR expression. Increased uptake mostly depends on the SSTR status of tumors; however, false-positive uptake can be demonstrated in benign diseases or other malignancies because of the increased SSTR expression. We present a case of a 50-year-old man with increased SSTR activity on cervical lesion located in internal jugular chain in 68Ga-DOTATATE PET/CT, which was performed for suspicion of paraganglioma. Biopsy revealed lymph node metastasis of squamous cell carcinoma other than paraganglioma. 18F-FDG PET/CT showed primary malignancy on larynx and lymph node metastasis, which were correlated surgically.

Sunitinib Treatment for Advanced Paraganglioma: Case Report of a Novel SDHD Gene Mutation Variant and Systematic Review of the Literature

Background

Paragangliomas (PGLs) are neuroendocrine neoplasms arising from chromaffin cells of sympathetic or parasympathetic paraganglia. Systemic therapies have been used only in metastatic PGLs. Antiangiogenic agents, such as sunitinib, could be a viable therapeutic choice in the subgroup of patients with SDH-positive PGLs. We describe the case of a man with Familial Paraganglioma Syndrome type 1 (FPGL) related to a novel mutation in SDHD gene treated with sunitinib. Furthermore, we performed a systematic review of the literature aimed to address the following question: is sunitinib treatment effective in patients with advanced/progressive/metastatic PGL?

Methods

We performed a data search using MEDLINE, Cochrane Library, and Scopus between April 2019 and September 2020. We included studies reporting data on clinical or biological characteristics, or clinical outcomes of patients with PGLs treated with sunitinib.

Results

The search leaded to the selection of 25 publications. Data from case reports and case series showed that disease control rate (DCR = stable disease + partial response + complete response) was achieved in 34.7% of cases under sunitinib treatment. In 39% of patients DCR was followed by progressive disease (PD) or tumor relapse, 26.1% patients showed PD. Data from clinical trials showed that DCR was 83%, and the median progression free survival was 13.4 months.

Discussion

Data from the present literature review suggested that sunitinib could be a viable therapeutic option in advanced/progressive/metastatic inoperable PGLs. However, further trials on the efficacy of sunitinib in FPGL and sporadic PGL are needed.

Neuroendocrine Tumor Theranostics: An Update and Emerging Applications in Clinical Practice

OBJECTIVE. Theranostics have shown great promise for delivering precision medicine, particularly in neuroendocrine tumors (NETs). The clinical applications of radiolabeled somatostatin analogues in imaging and radionuclide therapy have been rapidly increasing over the past 2 decades and are currently integrated into the management guidelines of NETs. This article summarizes the available literature on different somatostatin receptor-targeting radiopharmaceuticals with theranostic potential in NETs, pheochromocytomas, and paragangliomas. We discuss the clinical application, administration, and toxicity of recent FDA-approved radionuclide therapies, including ¹⁷⁷Lu-DOTATATE in advanced gastroenteropancreatic NETs and ¹³¹I-MIBG in advanced paragangliomas and pheochromocytomas. CONCLUSION. Several studies support the safety and clinical efficacy of peptide receptor radionuclide therapies in disease control and quality-of-life improvement in patients with NETs and report potential benefits of combined radionuclide treatment approaches. The utility and pitfalls of functional imaging in therapy response assessment and surveillance of NETs remain to be established.

Attenuation correction using deep Learning and integrated UTE/multi-echo Dixon sequence: evaluation in amyloid and tau PET imaging

PURPOSE

PET measures of amyloid and tau pathologies are powerful biomarkers for the diagnosis and monitoring of Alzheimer's disease (AD). Because cortical regions are close to bone, quantitation accuracy of amyloid and tau PET imaging can be significantly influenced by errors of attenuation correction (AC). This work presents an MR-based AC method that combines deep learning with a novel ultrashort time-to-echo (UTE)/multi-echo Dixon (mUTE) sequence for amyloid and tau imaging.

METHODS

Thirty-five subjects that underwent both 11C-PiB and 18F-MK6240 scans were included in this study. The proposed method was compared with Dixon-based atlas method as well as magnetization-prepared rapid acquisition with gradient echo (MPRAGE)- or Dixon-based deep learning methods. The Dice coefficient and validation loss of the generated pseudo-CT images were used for comparison. PET error images regarding standardized uptake value ratio (SUVR) were quantified through regional and surface analysis to evaluate the final AC accuracy.

RESULTS

The Dice coefficients of the deep learning methods based on MPRAGE, Dixon, and mUTE images were 0.84 (0.91), 0.84 (0.92), and 0.87 (0.94) for the whole-brain (above-eye) bone regions, respectively, higher than the atlas method of 0.52 (0.64). The regional SUVR error for the atlas method was around 6%, higher than the regional SUV error. The regional SUV and SUVR errors for all deep learning methods were below 2%, with mUTE-based deep learning method performing the best. As for the surface analysis, the atlas method showed the largest error (> 10%) near vertices inside superior frontal, lateral occipital, superior parietal, and inferior temporal cortices. The mUTE-based deep learning method resulted in the least number of regions with error higher than 1%, with the largest error (> 5%) showing up near the inferior temporal and medial orbitofrontal cortices.

CONCLUSION

Deep learning with mUTE can generate accurate AC for amyloid and tau imaging in PET/MR.

Metastatic Pheochromocytomas and Abdominal Paragangliomas

CONTEXT

Pheochromocytomas and paragangliomas (PPGLs) are believed to harbor malignant potential; about 10% to 15% of pheochromocytomas and up to 50% of abdominal paragangliomas will exhibit metastatic behavior.

EVIDENCE ACQUISITION

Extensive searches in the PubMed database with various combinations of the key words pheochromocytoma, paraganglioma, metastatic, malignant, diagnosis, pathology, genetic, and treatment were the basis for the present review.

DATA SYNTHESIS

To pinpoint metastatic potential in PPGLs is difficult, but nevertheless crucial for the individual patient to receive tailor-made follow-up and adjuvant treatment following primary surgery. A combination of histological workup and molecular predictive markers can possibly aid the clinicians in this aspect. Most patients with PPGLs have localized disease and may be cured by surgery. Plasma metanephrines are the main biochemical tests. Genetic testing is important, both for counseling and prognostic estimation. Apart from computed tomography and magnetic resonance imaging, molecular imaging using 68Ga-DOTATOC/DOTATATE should be performed. 123I-MIBG scintigraphy may be performed to determine whether 131I-MIBG therapy is a possible option. As first-line treatment in patients with metastatic disease, 177Lu-DOTATATE or 131I-MIBG is recommended, depending on which shows best expression. In patients with very low proliferative activity, watch-and-wait or primary treatment with long-acting somatostatin analogues may be considered. As second-line treatment, or first-line in patients with high proliferative rate, chemotherapy with temozolomide or cyclophosphamide + vincristine + dacarbazine is the therapy of choice. Other therapies, including sunitinib, cabozantinib, everolimus, and PD-1/PDL-1 inhibitors, have shown modest effect.

CONCLUSIONS

Metastatic PPGLs need individualized management and should always be discussed in specialized and interdisciplinary tumor boards. Further studies and newer treatment modalities are urgently needed.

Diagnosis for Pheochromocytoma and Paraganglioma: A Joint Position Statement of the Korean Pheochromocytoma and Paraganglioma Task Force

Pheochromocytoma and paraganglioma (PPGLs) are rare catecholamine-secreting neuroendocrine tumors but can be life-threatening. Although most PPGLs are benign, approximately 10% have metastatic potential. Approximately 40% cases are reported as harboring germline mutations. Therefore, timely and accurate diagnosis of PPGLs is crucial. For more than 130 years, clinical, molecular, biochemical, radiological, and pathological investigations have been rapidly advanced in the field of PPGLs. However, performing diagnostic studies to localize lesions and detect metastatic potential can be still challenging and complicated. Furthermore, great progress on genetics has shifted the paradigm of genetic testing of PPGLs. The Korean PPGL task force team consisting of the Korean Endocrine Society, the Korean Surgical Society, the Korean Society of Nuclear Medicine, the Korean Society of Pathologists, and the Korean Society of Laboratory Medicine has developed this position statement focusing on the comprehensive and updated diagnosis for PPGLs.

Misleading 68 GALLIUM-dotatate PET scan in a patient with a history of a phaeochromocytoma: Unsuspected uptake in papillary thyroid carcinoma metastases

Scanning for somatostatin receptors using 68 Ga-dotatate positron emission tomography with co-registration with computed tomography or magnetic resonance imaging is now in widespread use for the identification of neuroendocrine tumours, phaeochromocytomas, and paragangliomas and their metastases. We present a case where a patient with a phaeochromocytoma showed uptake in her neck considered diagnostic of a head-and-neck paraganglioma, which was subsequently confirmed to be a metastatic papillary thyroid carcinoma. We alert clinicians to such falsely-identified tumours using this extensively used imaging technique.

A 10-year observational single-center study of retroperitoneal unicentric Castleman disease

Diagnosis of unicentric Castleman disease (UCD) is not easy before the resection and obtainment of pathological result. We retrospectively summarized 10-year experience of clinical evaluation and management for retroperitoneal UCD in Peking Union Medical College Hospital (PUMCH) between December 1, 2009 and December 31, 2019. Seventy two UCD patients with pathological diagnosis after resection were screened out. Among them 25 patients had retroperitoneal UCD. The average age of the 25 patients was 43.80 ± 12.79, and 52.00% were male. No patients had systemic symptoms, and 1 patient got preoperative treatment. The average size of masses was 5.59 ± 2.86 cm. The UCD sites included kidney, adrenal area, perinephric area, pancreas, peripancreatic area, area of descending part of duodenum, periaortic area or beside iliac artery, and others. The masses presented different degree of enhancement on CT scans and hypoecho or isoecho on ultrasound. Increased metabolism could be found on 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT). Some patients had positive results on somatostatin receptor imaging, but none had positive results on 131I-metaiiodo-benzylguanidine (131I-MIBG). Some patients presented the elevated level of interleukin-6 (IL-6), 24hour-urinary catecholamine and tumor markers. All the patients received complete resection of masses and 96.00% had hyaline-vascular type pathology except 1 patient (plasma cell-type). Ninety two percent patients received a long-term follow-up with an average follow-up time of 35.48 ± 33.90 months. No patients died or experienced relapse during follow-up. Differential diagnosis of retroperitoneal UCD may be difficult according to imaging and laboratorial examinations. Differential diagnosis with pheochromocytomas/paragangliomas should be taken into special consideration. Different imaging examinations, such as CT/MRI, 18F-PET/CT, somatostatin receptor imaging and 131I-MIBG, can be combined for differential analysis. Complete resection is the best treatment and could provide a final pathological diagnosis.

Screening of a Large Cohort of Asymptomatic SDHx Mutation Carriers in Routine Practice

CONTEXT

When an SDHx mutation is identified in a patient with a pheochromocytoma (PCC) or a paraganglioma (PGL), predictive genetic testing can detect mutation carriers that would benefit from screening protocols.

OBJECTIVE

To define the tumor detection rate in a large cohort of asymptomatic SDHX mutation carriers.

DESIGN AND SETTING

Retrospective multicentric study in 6 referral centers.

PATIENTS

Between 2005 and 2019, 249 asymptomatic SDHx (171 SDHB, 31 SDHC, 47 SDHD) mutation carriers, with at least 1 imaging work-up were enrolled.

RESULTS

Initial work-up, including anatomical (98% of subjects [97-100% according to center]) and/or functional imaging (67% [14-90%]) detected 48 tumors in 40 patients. After a negative initial work-up, 124 patients benefited from 1 to 9 subsequent follow-up assessments (mean: 1.9 per patient), with a median follow-up time of 5 (1-13) years. Anatomical (86% [49-100 %]) and/or functional imaging (36% [7-60 %]) identified 10 new tumors (mean size: 16 mm [4-50]) in 10 patients. Altogether, 58 tumors (55 paraganglioma [PGL], including 45 head and neck PGL, 2 pheochromocytoma [PCC], 1 gastrointestinal stromal tumor [GIST]), were detected in 50 patients (22 [13%] SDHB, 1 [3.2%] SDHC, and 27 [57%] SDHD), with a median age of 41 years old [11-86], 76% without catecholamine secretion and 80% during initial imaging work-up.

CONCLUSIONS

Imaging screening enabled detection of tumors in 20% of asymptomatic SDHx mutation carriers, with a higher detection rate in SDHD (57%) than in SDHB (13%) and SDHC (3%) mutation carriers, arguing for a gene-by-gene approach. Prospective studies using well-defined protocols are needed to obtain strong and useful data.

Head and neck paragangliomas in Norway, importance of genetics, updated diagnostic workup and treatment

BACKGROUND

Head and neck paragangliomas (HNPG) are rare and predominantly benign tumours, originating from the neuroendocrine paraganglionic system. A considerable proportion of HNPGs are hereditary, depending on the population.

AIMS/OBJECTIVES

The purpose of this study was to estimate the rate of hereditary HNPGs in a Scandinavian (Norwegian) population, report long-term experience with HNPGs and offer all patients diagnosed an updated follow-up, with emphasis on identifying hereditary HNPGs through genetic screening and multifocality by 18 F-2-fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT).

MATERIAL AND METHODS

Our study was a partly retrospective and partly prospective cohort study. It included patients with HNPG diagnosed at Oslo University Hospital (OUH), Rikshospitalet between 1990 and 2017. The patients underwent genetic testing, ¹⁸F-FDG PET/CT and measurement of catecholamines and meta-nephrines in the plasma. All resection specimens and biopsies were subjected to histopathological review. The genetic testing protocol consisted of testing for mutations in the following genes; SDHD, SDHB, SDHC, VHL and RET.

RESULTS

Sixty-three patients were included in the study with a median age of 49 years (range 12 - 80). Cranial nerve dysfunction was present upon diagnosis in 13%, and 14% had multifocal paraganglioma (PG) disease. Fifty-six patients (89% of all the patients) underwent genetic testing, and 29% of these had a PG related mutation. Seven of the eight patients (88%) with multifocal PGs who underwent genetic testing had a mutation. In two of the patients, the ¹⁸F-FDG PET/CT revealed unknown and subclinical multifocality.

CONCLUSIONS AND SIGNIFICANCE

This is the first study with systematic genetic workup and PET/CT imaging in Scandinavia of HNPG patients. The mutation rate was within the lower range reported in the literature with respect to HNPGs. Combining genetic testing and PET/CT imaging in the diagnostic workup of HNPGs is valuable.

Consensus on molecular imaging and theranostics in neuroendocrine neoplasms

Nuclear medicine plays an increasingly important role in the management neuroendocrine neoplasms (NEN). Somatostatin analogue (SSA)-based positron emission tomography/computed tomography (PET/CT) and peptide receptor radionuclide therapy (PRRT) have been used in clinical trials and approved by the European Medicines Agency (EMA) and the US Food and Drug Administration (FDA). European Association of Nuclear Medicine (EANM) Focus 3 performed a multidisciplinary Delphi process to deliver a balanced perspective on molecular imaging and radionuclide therapy in well-differentiated neuroendocrine tumours (NETs). NETs form in cells that interact with the nervous system or in glands that produce hormones. These cells, called neuroendocrine cells, can be found throughout the body, but NETs are most often found in the abdomen, especially in the gastrointestinal tract. These tumours may also be found in the lungs, pancreas and adrenal glands. In addition to being rare, NETs are also complex and may be difficult to diagnose. Most NETs are non-functioning; however, a minority present with symptoms related to hypersecretion of bioactive compounds. NETs often do not cause symptoms early in the disease process. When diagnosed, substantial number of patients are already found to have metastatic disease. Several societies' guidelines address Neuroendocrine neoplasms (NENs) management; however, many issues are still debated, due to both the difficulty in acquiring strong clinical evidence in a rare and heterogeneous disease and the different availability of diagnostic and therapeutic options across countries. EANM Focus 3 reached consensus on employing ⁶⁸gallium-labelled somatostatin analogue ([⁶⁸Ga]Ga-DOTA-SSA)-based PET/CT with diagnostic CT or magnetic resonance imaging (MRI) for unknown primary NET detection, metastatic NET, NET staging/restaging, suspected extra-adrenal pheochromocytoma/paraganglioma and suspected paraganglioma. Consensus was reached on employing ¹⁸fluorine-fluoro-2-deoxyglucose ([¹⁸F]FDG) PET/CT in neuroendocrine carcinoma, G3 NET and in G1-2 NET with mismatched lesions (CT-positive/[⁶⁸Ga]Ga-DOTA-SSA-negative). Peptide receptor radionuclide therapy (PRRT) was recommended for second line treatment for gastrointestinal NET with [⁶⁸Ga]Ga-DOTA-SSA uptake in all lesions, in G1/G2 NET at disease progression, and in a subset of G3 NET provided all lesions are positive at [¹⁸F]FDG and [⁶⁸Ga]Ga-DOTA-SSA. PRRT rechallenge may be used for in patients with stable disease for at least 1 year after therapy completion. An international consensus is not only a prelude to a more standardised management across countries but also serves as a guide for the direction to follow when designing new research studies.

High-specific-activity 131iodine-metaiodobenzylguanidine for therapy of unresectable pheochromocytoma and paraganglioma

Pheochromocytomas and paragangliomas (PPG) are rare cancers arising from the adrenal medulla (pheochromocytoma) or autonomic ganglia (paraganglioma). They have highly variable biological behavior. Most PPG express high-affinity norepinephrine transporters, allowing active uptake of the norepinephrine analog, ¹³¹iodine-metaiodobenzylguanidine (¹³¹I-MIBG). Low-specific-activity forms of ¹³¹I-MIBG have been used since 1983 for therapy of PPG. High-specific-activity ¹³¹I-MIBG therapy improves hypertension management, induces partial radiological response or stable disease, decreases biochemical markers of disease activity and is well tolerated by patients. This drug, approved in the USA in July 2018, is the first approved agent for patients with unresectable, locally advanced or metastatic PPG and imaging evidence of metaiodobenzylguanidine uptake, who require systemic anticancer therapy.

The utility of 68Ga-DOTATATE PET/CT in localizing primary/metastatic pheochromocytoma and paraganglioma in children and adolescents - a single-center experience

OBJECTIVES

Pediatric pheochromocytoma and paraganglioma (PPGL) are rare tumors with limited data on the diagnostic performance of ⁶⁸Ga-DOTA(0)-Tyr(3)-octreotate positron emission tomography-computed tomography (⁶⁸Ga-DOTATATE PET/CT). We have described our experience of ⁶⁸Ga-DOTATATE PET/CT in overall and von Hippel Lindau (VHL)-associated pediatric PPGL and compared its sensitivity with that of ¹³¹I-meta-iodobenzyl-guanidine (¹³¹I-MIBG), ¹⁸F-fluorodeoxyglucose PET/CT (¹⁸F-FDG PET/CT), and contrast-enhanced CT (CECT).

METHODS

Retrospective evaluation of consecutive PPGL patients (age: ≤20 years), who had undergone at least one functional imaging [¹³¹I-MIBG, ¹⁸F-FDG PET/CT, and/or ⁶⁸Ga-DOTATATE PET/CT], was done. Composite of anatomical and all the performed functional imaging scans, image comparator (IC), was considered as the gold standard for sensitivity analysis.

RESULTS

In a cohort of 32 patients (16 males, age at diagnosis: 16.4 ± 2.68 years), lesion-wise sensitivity of ⁶⁸Ga-DOTATATE PET/CT (95%) was higher than that of both ¹⁸F-FDG-PET/CT (80%, p=0.027) and ¹³¹I-MIBG (65%, p=0.0004) for overall lesions, than that of ¹⁸F-FDG-PET/CT (100 vs. 67%, p=0.017) for primary PPG, and than that of ¹³¹I-MIBG (93 vs. 42%, p=0.0001) for metastases. In the VHL (n=14), subgroup, ⁶⁸Ga-DOTATATE PET/CT had higher lesion-wise sensitivity (100%) compared to ¹⁸F-FDG PET/CT (74%, p=0.045) and ¹³¹I-MIBG (64%, p=0.0145).

CONCLUSIONS

In our pediatric PPGL cohort, overall lesion-wise sensitivity of ⁶⁸Ga-DOTATATE PET/CT was higher than that of ¹⁸F-FDG PET/CT and ¹³¹I-MIBG scintigraphy. Hence, we recommend ⁶⁸Ga-DOTATATE PET/CT as the preferred modality in pediatric PPGL. ⁶⁸Ga-DOTATATE PET/CT may evolve as a preferred imaging modality for disease surveillance in VHL.

Somatostatin receptor-positive breast lesions on 68Ga-DOTATATE PET/CT

OBJECTIVE

This study sets out to evaluate patients with increased uptake in breast lesions on ⁶⁸Ga-DOTATATE PET/CT (DOTA PET) and determine the clinical significance of somatostatin receptor (SSTR) positive breast lesions.

METHODS

We retrospectively evaluated all patients with increased SSTR uptake in breast lesions on DOTA PET. Patients with physiological (e.g., lactation) or normal variant breast uptake (e.g., mild diffuse glandular uptake) were excluded. The maximum standard uptake value (SUVmax) was calculated using a manually drawn region of interest in the most intense uptake of breast lesions. All lesions were correlated with breast imaging, including mammography and ultrasonography. Histopathological correlation was performed if the lesion was suspicious for malignancy. Lesions were followed up radiologically (1-8 years).

RESULTS

Out of 1573 retrospectively analyzed DOTA PET scans, the incidence of SSTR + breast lesions was measured as 1.1% (n = 18); however, 4 of 18 patients were excluded due to the lack of final diagnosis of lesions. The median age was 35 (range 14-58 years), and all patients were female. The median SUVmax of SSTR + breast lesions was 5.2 (range 1.5-12.6) for a total of 14 patients. Twelve patients had a single SSTR + breast lesion, while 2 patients had multiple SSTR + lesions on bilateral breasts. In 6 patients, single SSTR + lesions were considered as fibroadenoma; in 2 patients, multiple SSTR + lesions were considered as metastases of NET, based on correlative breast imaging. In 6 patients, histopathological confirmation was needed for the final diagnosis. Histopathologic findings confirmed fibroadenoma in 4 patients by biopsy, in 1 patient with surgical removal of the lesion. The last patient who had a history of IDC was diagnosed with a recurrence of IDC with biopsy. The median SUVmax was 5.1 (range 1.5-9.4) for malignant breast lesions and 5.4 (range 2.2-12.6) for benign breast lesions.

CONCLUSION

SSTR + breast lesions on DOTA PET are rarely seen in clinical practice. Uptakes of breast lesions in our cases were variable and not useful for differential diagnosis of lesions. It seems that SSTR + breast lesions should be evaluated with clinical and radiological characteristics, and correlative breast imaging and/or histopathological verification should be performed for suspicious lesions to avoid misdiagnosis.

The utility of 68ga-dotatate pet/ct in localizing primary/metastatic pheochromocytoma and paraganglioma: Asian Indian experience

Purpose:

Pheochromocytoma and paraganglioma (PGL), together called PPGL, are rare tumors with a limited number of studies on the diagnostic performance of ⁶⁸Ga-DOTA (0)-Tyr (3)-octreotate positron emission tomography-computed tomography (⁶⁸Ga-DOTATATE PET/CT) from the Asian-Indian subcontinent.

Materials and Methods:

In this retrospective study, PPGL suspects (n = 87) who had undergone at least contrast-enhanced computed tomography (CECT) and ⁶⁸Ga-DOTATATE PET/CT, were included. Lesion-wise, patient-wise, and region-wise sensitivities of ⁶⁸Ga-DOTATATE PET/CT, ¹⁸F fluorodeoxyglucose positron emission tomography CT (¹⁸F-FDG PET/CT, n = 53), ¹³¹I-metaiodobenzylguanidine (¹³¹I-MIBG, n = 37), and CECT were compared, and diagnostic performance of ⁶⁸Ga-DOTATATE PET/CT in the detection of PPGL was calculated.

Results:

⁶⁸Ga-DOTATATE PET/CT had significantly higher lesion-wise sensitivity than ¹³¹I-MIBG for both primary (94% vs 75%, P = 0.004) and metastatic disease (85% vs 59%, P = 0.001) and higher sensitivity than CECT for metastatic lesions (83% vs 43%, P = 0.0001). The lesion-wise sensitivity of ⁶⁸Ga-DOTATATE PET/CT was similar to ¹⁸F-FDG PET/CT for both primary tumors (94% vs 85%, P = 0.08) and metastatic lesions (82% vs 84%, P = 0.76) in the whole cohort but tended to be inferior in the head to head comparison.

Conclusion:

⁶⁸Ga-DOTATATE PET/CT had higher sensitivity for detection of PPGL than ¹³¹I-MIBG (primary and metastatic) and CECT (metastatic) but similar to ¹⁸F-FDG PET/CT (primary and metastatic).

A Solitary Skull Base Plasmacytoma Mimicking Paraganglioma on 68Ga-DOTATATE PET/CT

The patient was a 61-year-old man with a history of neck pain starting around October 2019. CT of the neck showed a lytic lesion at the right skull base. Subsequent MRI demonstrated an enhancing destructive mass in the right skull base centered in the occipital bone and condyle involving the jugular foramen and hypoglossal canal. An F-FDG PET/CT was performed showing increased FDG uptake in the right jugular foramen tumor. In addition, a PET/CT with Ga-[DOTA-Tyr3]-octreotate (Ga-DOTATATE) demonstrated a Ga-DOTATATE-avid lesion in the right jugular foramen eroding the adjacent osseous structures. Biopsy revealed a plasmacytoma and not paraganglioma.

Carney Triad, Carney-Stratakis Syndrome, 3PAS and Other Tumors Due to SDH Deficiency

Succinate dehydrogenase (SDH) is a key respiratory enzyme that links Krebs cycle and electron transport chain and is comprised of four subunits SDHA, SDHB, SDHC and SDHD. All SDH-deficient tumors are caused by or secondary to loss of SDH activity. As many as half of the familial cases of paragangliomas (PGLs) and pheochromocytomas (PHEOs) are due to mutations of the SDHx subunits. Gastrointestinal stromal tumors (GISTs) associated with SDH deficiency are negative for KIT/PDGFRA mutations and present with distinctive clinical features such as early onset (usually childhood or adolescence) and almost exclusively gastric location. SDH-deficient GISTs may be part of distinct clinical syndromes, Carney-Stratakis syndrome (CSS) or dyad and Carney triad (CT). CSS is also known as the dyad of GIST and PGL; it affects both genders equally and is inherited in an autosomal dominant manner with incomplete penetrance. CT is a very rare disease; PGL, GIST and pulmonary chondromas constitute CT which shows female predilection and may be a mosaic disorder. Even though there is some overlap between CT and CSS, as both are due to SDH deficiency, CSS is caused by inactivating germline mutations in genes encoding for the SDH subunits, while CT is mostly caused by a specific pattern of methylation of the SDHC gene and may be due to germline mosaicism of the responsible genetic defect.

Somatostatin Receptors and Analogs in Pheochromocytoma and Paraganglioma: Old Players in a New Precision Medicine World

Neuroendocrine tumors overexpress somatostatin receptors, which serve as important and unique therapeutic targets for well-differentiated advanced disease. This overexpression is a well-established finding in gastroenteropancreatic neuroendocrine tumors which has guided new medical therapies in the administration of somatostatin analogs, both "cold", particularly octreotide and lanreotide, and "hot" analogs, chelated to radiolabeled isotopes. The binding of these analogs to somatostatin receptors effectively suppresses excess hormone secretion and tumor cell proliferation, leading to stabilization, and in some cases, tumor shrinkage. Radioisotope-labeled somatostatin analogs are utilized for both tumor localization and peptide radionuclide therapy, with ⁶⁸Ga-DOTATATE and ¹⁷⁷Lu-DOTATATE respectively. Benign and malignant pheochromocytomas and paragangliomas also overexpress somatostatin receptors, irrespective of embryological origin. The pattern of somatostatin receptor overexpression is more prominent in succinate dehydrogenase subunit B gene mutation, which is more aggressive than other subgroups of this disease. While the Food and Drug Administration has approved the use of ⁶⁸Ga-DOTATATE as a radiopharmaceutical for somatostatin receptor imaging, the use of its radiotherapeutic counterpart still needs approval beyond gastroenteropancreatic neuroendocrine tumors. Thus, patients with pheochromocytoma and paraganglioma, especially those with inoperable or metastatic diseases, depend on the clinical trials of somatostatin analogs. The review summarizes the advances in the utilization of somatostatin receptor for diagnostic and therapeutic approaches in the neuroendocrine tumor subset of pheochromocytoma and paraganglioma; we hope to provide a positive perspective in using these receptors as targets for treatment in this rare condition.

131I-metaiodobenzylguanidine and peptide receptor radionuclide therapy in pheochromocytoma and paraganglioma

PURPOSE OF REVIEW

Pheochromocytomas and paragangliomas are rare tumors arising, respectively, from the adrenal medulla and extra-adrenal sympathetic or parasympathetic paraganglia. The main therapeutic objectives in case of metastatic disease are the reduction of tumor burden and the control of symptoms resulting from excessive catecholamine secretion. Treatment choices constitute not only a wait and see attitude, locoregional approaches, chemotherapy regiments but also radiopharmaceutical agents, and they should be discussed in a specialized multidisciplinary board. This review will briefly discuss the radiopharmaceutical modalities in patients with pheochromocytomas and paragangliomas (I-MIBG and PRRT).

RECENT FINDINGS

I-MIBG (Azedra) has received FDA approval for patients with iobenguane-scan-positive, unresectable, locally advanced or metastatic pheochromocytomas and paragangliomas who require systemic anticancer therapy, whereas peptide receptor radionuclide therapy using radiolabelled somatostatin analogues is currently performed in compassionate use, with very promising results. No prospective head-to-head comparison between the modalities has been conducted to date.

SUMMARY

Promising results have been reported for both radiopharmaceutical agents, mostly in the setting of retrospective series. No prospective head-to-head comparison between the modalities is yet available.

The impact of Ga-68 DOTATATE PET/CT imaging on management of patients with paragangliomas

OBJECTIVE

Paragangliomas are rare tumours of neural crest origin that express high levels of somatostatin receptor. Ga-68 DOTATATE PET/CT is a widely accepted method for imaging of neuroendocrine tumours. This study was performed to review a Ga-68 DOTATATE PET/CT patient database and to establish the impact of the modality on patient treatment.

METHODS

Demographic data, imaging data and change in management after Ga-68 DOTATATE PET/CT were evaluated.

RESULTS

Ga-68 DOTATATE PET/CT scans were performed in 21 patients in whom paragangliomas had been confirmed after biopsy or surgery and in one patient with suspected paraganglioma. In most patients, the primary site was the organ of Zuckerkandl (12/22). Of the 22 Ga-68 DOTATATE PET/CT scans completed, 19 (86.4%) were positive and three (13.6%) negative. In 12 of 14 recurrent cases (90.9%), the treatment plan was changed after the Ga-68 DOTATATE PET/CT scan owing to new, unexpected findings, while it remained unchanged in two (9.1%). Regarding the change in treatment plan, in most instances the new treatment comprised peptide receptor radionuclide therapy (PRRT).

CONCLUSION

Ga-68 DOTATATE PET/CT findings led to a change in the scheduled treatment plan in 90.9% of patients with suspected recurrence. The most frequent change consisted in initiation of PRRT due to disease recurrence or progression or detection of multiple metastases.

68Ga-DOTATATE PET/MRI for Neuroendocrine Tumors: A Pictorial Review

Neuroendocrine tumors (NETs) constitute a variety of neoplastic entities and exhibit variable degrees of neuroendocrine differentiation and phenotypes, as well as genetic profiles. Ga-DOTATATE PET is a novel imaging technique for NET. Although PET/CT is commonly utilized for oncologic imaging, PET/MRI is particularly suited for NETs, as MRI provides greater soft tissue contrast than CT, allowing for improved detection and characterization of NETs, particularly when liver metastasis is suspected or needs to be ruled out. The current pictorial review aims to illustrate the complementary advantages, as well as pitfalls of Ga-DOTATATE PET/MRI in the evaluation of NETs.

Multimodality Imaging of Neuroendocrine Tumors

Neuroendocrine tumors are rare solid tumors with an estimated 12,000 people in the United States diagnosed each year. Neuroendocrine tumors can occur in any part of the body. There is a wide spectrum of disease, ranging from slow-growing and indolent tumors found incidentally to highly aggressive malignancies with a poor prognosis. Knowledge of neuroendocrine tumor pathology is essential in the diagnostic workup of these patients. This article focuses on the evaluation, detection, and staging of common neuroendocrine tumors with multiple imaging modalities; the information gained with a multimodality approach is often complementary and leads to image-guided treatment decision making.

Pheochromocytoma and Paraganglioma: From Clinical Findings to Diagnosis

The majority of pheochromocytoma (PCC) and paraganglioma (PGL) are endocrine active tumors, and they cause clinical symptoms by secreting excess one or more catecholamines (epinephrine, norepinephrine, and dopamine) and their inactive metabolites (metanephrine, normetanephrine, 3-metoxythromine). Although signs and symptoms regarding excess catecholamine often develop in PCC and PGL (PPGL), non-functional PPGLs may present with local compression symptoms. Persistent, sometimes worsening hypertension is the most common finding and occurs in 80-90% of the patients. Classically defined symptom triad; headache, sweating and palpitations are seen in only 25% of the patients with PCC. The difference of clinical symptoms may be related to the tumor secretion, epinephrine or norepinephrine. All patients with signs and symptoms suggestive of catecholamine excess should be screened by biochemical tests regardless of whether they have hypertension or not. Not all patients with newly diagnosed hypertension need to be screened, but only patients with additional tips for catecholamine excess should be screened. Approximately 20% of the PPGLs are diagnosed in childhood, and the male/female ratio is 2/1. 60-90% of pediatric patients present with hypertension. PPGL in pregnancy is rare, and the estimated incidence ranges between 1/15000-1/54000. Although early diagnosis is the most important factor in preventing mortality, diagnosis is not as easy as it is a rare condition. Hypertension is a common complication in pregnancy, occurring in 5-10%. Computed tomography should not be used as the imaging method during pregnancy; the first choice is magnetic resonance imaging with gadolinium or without contrast. Plasma free metanephrine or 24-hour urinary fractionated metanephrine level is recommended as a screening test for the diagnosis of PPGL in the Endocrine Society Clinical Practice Guideline. In suspicious situations, tests should be repeated. Since 40% of these patients have germline mutations, genetic tests are recommended for all patients with PPGL regardless of family history and age. Preoperative knowledge of germline mutations affects the surgical approach and the extent of adrenalectomy. After the biochemical diagnosis is made in PPGL, the tumor is localized with imaging methods to make the operation plan. In this review, we aimed to evaluate the clinical findings, diagnostic tests, and imaging studies for tumor localization in PPGL.