Outcomes of annual surveillance imaging in an adult and paediatric cohort of succinate dehydrogenase B mutation carriers

Biochemical Assessment of Pheochromocytoma and Paraganglioma

Pheochromocytoma and paraganglioma (PPGL) require prompt consideration and efficient diagnosis and treatment to minimize associated morbidity and mortality. Once considered, appropriate biochemical testing is key to diagnosis. Advances in understanding catecholamine metabolism have clarified why measurements of the O-methylated catecholamine metabolites rather than the catecholamines themselves are important for effective diagnosis. These metabolites, normetanephrine and metanephrine, produced respectively from norepinephrine and epinephrine, can be measured in plasma or urine, with choice according to available methods or presentation of patients. For patients with signs and symptoms of catecholamine excess, either test will invariably establish the diagnosis, whereas the plasma test provides higher sensitivity than urinary metanephrines for patients screened due to an incidentaloma or genetic predisposition, particularly for small tumors or in patients with an asymptomatic presentation. Additional measurements of plasma methoxytyramine can be important for some tumors, such as paragangliomas, and for surveillance of patients at risk of metastatic disease. Avoidance of false-positive test results is best achieved by plasma measurements with appropriate reference intervals and preanalytical precautions, including sampling blood in the fully supine position. Follow-up of positive results, including optimization of preanalytics for repeat tests or whether to proceed directly to anatomic imaging or confirmatory clonidine tests, depends on the test results, which can also suggest likely size, adrenal vs extra-adrenal location, underlying biology, or even metastatic involvement of a suspected tumor. Modern biochemical testing now makes diagnosis of PPGL relatively simple. Integration of artificial intelligence into the process should make it possible to fine-tune these advances.

Surveillance Improves Outcomes for Carriers of SDHB Pathogenic Variants: A Multicenter Study

CONTEXT

Carriers of succinate dehydrogenase type B (SDHB) pathogenic variants (PVs) are at risk of pheochromocytoma and paraganglioma (PPGL) from a young age. It is widely recommended carriers enter a surveillance program to detect tumors, but there are limited studies addressing outcomes of surveillance protocols for SDHB PV carriers.

OBJECTIVE

The purpose of this study was to describe surveillance-detected (s-d) tumors in SDHB PV carriers enrolled in a surveillance program and to compare their outcomes to probands.

METHODS

This was a multicenter study of SDHB PV carriers with at least 1 surveillance episode (clinical, biochemical, imaging) in Australian genetics clinics. Data were collected by both retrospective and ongoing prospective follow-up. Median duration of follow-up was 6.0 years.

RESULTS

181 SDHB PV carriers (33 probands and 148 nonprobands) were assessed. Tumors were detected in 20% of nonprobands undergoing surveillance (age range 9-76 years). Estimated 10-year metastasis-free survival was 66% for probands and 84% for nonprobands with s-d tumors (P = .027). S-d tumors were smaller than those in probands (median 27 mm vs 45 mm respectively, P = .001). Tumor size ≥40 mm was associated with progression to metastatic disease (OR 16.9, 95% CI 2.3-187.9, P = .001). Patients with s-d tumors had lower mortality compared to probands: 10-year overall survival was 79% for probands and 100% for nonprobands (P = .029).

CONCLUSION

SDHB carriers with s-d tumors had smaller tumors, reduced risk of metastatic disease, and lower mortality than probands. Our results suggest that SDHB PV carriers should undertake surveillance to improve clinical outcomes.

Personalized Management of Pheochromocytoma and Paraganglioma

Pheochromocytomas/paragangliomas are characterized by a unique molecular landscape that allows their assignment to clusters based on underlying genetic alterations. With around 30% to 35% of Caucasian patients (a lower percentage in the Chinese population) showing germline mutations in susceptibility genes, pheochromocytomas/paragangliomas have the highest rate of heritability among all tumors. A further 35% to 40% of Caucasian patients (a higher percentage in the Chinese population) are affected by somatic driver mutations. Thus, around 70% of all patients with pheochromocytoma/paraganglioma can be assigned to 1 of 3 main molecular clusters with different phenotypes and clinical behavior. Krebs cycle/VHL/EPAS1-related cluster 1 tumors tend to a noradrenergic biochemical phenotype and require very close follow-up due to the risk of metastasis and recurrence. In contrast, kinase signaling-related cluster 2 tumors are characterized by an adrenergic phenotype and episodic symptoms, with generally a less aggressive course. The clinical correlates of patients with Wnt signaling-related cluster 3 tumors are currently poorly described, but aggressive behavior seems likely. In this review, we explore and explain why cluster-specific (personalized) management of pheochromocytoma/paraganglioma is essential to ascertain clinical behavior and prognosis, guide individual diagnostic procedures (biochemical interpretation, choice of the most sensitive imaging modalities), and provide personalized management and follow-up. Although cluster-specific therapy of inoperable/metastatic disease has not yet entered routine clinical practice, we suggest that informed personalized genetic-driven treatment should be implemented as a logical next step. This review amalgamates published guidelines and expert views within each cluster for a coherent individualized patient management plan.

Tumour detection and outcomes of surveillance screening in SDHB and SDHD pathogenic variant carriers

OBJECTIVE

Succinate dehydrogenase subunit (SDHx) pathogenic variants predispose to phaeochromocytoma and paraganglioma (PPGL). Lifelong surveillance is recommended for all patients to enable prompt detection and treatment. There is currently limited evidence for optimal surveillance strategies in hereditary PPGL. We aim to detail the clinical presentation of PPGL in our cohort of non-index SDHB and SDHD pathogenic variant carriers.

METHODS

Retrospective analysis of medical and genetic records from a single tertiary referral centre identified SDHB or SDHD pathogenic variants in 74 non-index cases (56 SDHB and 18 SDHD). Surveillance screening for asymptomatic relatives consisted of annual plasma metanephrine measurement and whole-body MRI with contrast at 3-5 yearly intervals.

RESULTS

Twenty-three out of 74 non-index patients (10 SDHB and 13 SDHD) were diagnosed with PPGL, 17 patients through surveillance screening (24 tumours in total) and 6 diagnosed prior to commencement of cascade screening with symptomatic presentation. MRI with contrast identified PPGL in 22/24 screen-detected tumours and 5/24 tumours had elevated plasma metanephrine levels. Penetrance in non-index family members was 15.2 and 47.2% for SDHB carriers and 71.6 and 78.7% for SDHD carriers at age of 50 and 70 years, respectively.

CONCLUSION

Surveillance screening with combined biochemical testing and imaging enables early detection of PPGL in asymptomatic relatives with SDHx pathogenic variants. The presence of disease at first screen was significant in our cohort and hence further multi-centre long-term data are needed to inform counselling of family members undergoing lifelong surveillance.

Imaging evaluation of hereditary renal tumors: a pictorial review

More than 10 hereditary renal tumor syndromes (HRTSs) and related germline mutations have been reported with HRTS-associated renal and extrarenal manifestations with benign and malignant tumors. Radiologists play an important role in detecting solitary or multiple renal masses with or without extrarenal findings on imaging and may raise the possibility of an inherited predisposition to renal cell carcinoma, providing direction for further screening, intervention and surveillance of the patients and their close family members before the development of potentially lethal renal and extrarenal tumors. Renal cell carcinomas (RCCs) associated with von Hippel-Lindau disease are typically slow growing while RCCs associated with HRTSs, such as hereditary leiomyomatosis and renal cell carcinoma syndrome, are highly aggressive. Therefore, radiologists need to be familiar with clinical and imaging findings of renal and extrarenal manifestations of HRTSs. This article reviews clinical and imaging findings for the evaluation of patients with well-established HRTSs from a radiologist's perspective to facilitate the clinical decision-making process for patient management.

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.

Characteristics of germline mutations in Korean patients with pheochromocytoma/paraganglioma

BACKGROUND

Pheochromocytomas and paragangliomas (PPGLs) are catecholamine-producing neuroendocrine tumours. PPGLs are a rare but important cause of secondary hypertension owing to their high morbidity and mortality. Patients with PPGL exhibit an increased prevalence of mutations in one of the PPGL susceptibility genes according to previous studies. We aimed to investigate the characteristics of germline mutations in the largest number of Korean patients with PPGL.

METHODS

In this study, 161 patients with PPGL were evaluated. Phenotype data, including biochemical, pathological and anatomical imaging results, were collected. Germline mutations in 10 PPGL-related genes were tested by targeted next-generation sequencing (NGS), Sanger sequencing and multiplex ligation-dependent probe amplification.

RESULTS

Approximately 21% of apparently sporadic PPGLs harboured germline mutations of the PPGL-related genes. The mutation carriers were younger at the first diagnosis and had more bilateral (28.6% vs 4.0%, p<0.001) and multifocal (11.4% vs 1.6%, p=0.027) PPGLs, but showed no metastatic risk (17.1% vs 11.1%, p=0.504), than non-mutation carriers. Missense mutation of SDHD p.V111I was found in this cohort of Asian patients, which was associated with unilateral pheochromocytoma with dominantly epinephrine production.

CONCLUSION

This study covered the largest number of Korean patients with PPGL. To our knowledge, it is the first to compare results of targeted NGS panel with those of conventional sequencing methods in Asia. We demonstrated that the variant type, as well as the mutated gene, may determine the phenotype and prognosis of PPGLs.

Update on the Genetics of Pituitary Tumors

Pituitary adenomas are common intracranial neoplasms, with diverse phenotypes. Most of these tumors occur sporadically and are not part of genetic disorders. Over the last decades numerous genetic studies have led to identification of somatic and germline mutations associated with pituitary tumors, which has advanced the understanding of pituitary tumorigenesis. Exploring the genetic background of pituitary neuroendocrine tumors can lead to early diagnosis associated with better outcomes, and their molecular mechanisms should lead to novel targeted therapies even for sporadic tumors. This article summarizes the genes and the syndromes associated with pituitary tumors.

Surveillance of succinate dehydrogenase gene mutation carriers: Insights from a nationwide cohort

OBJECTIVE

Mutations in the genes coding for succinate dehydrogenase (SDHx) are the most frequent germline alterations in pheochromocytomas and paragangliomas. Evidence for the advantages associated with presymptomatic screening for SDHx mutation carriers is scarce. This study describes a nationwide cohort of these mutation carriers and aims to compare patients with clinical manifestations of the disease and those diagnosed through genetic screening.

DESIGN

Cross-sectional study.

PATIENTS

SDHx mutation carriers (n = 118) followed through the Portuguese Oncology referral centres: 41 probands and 77 nonprobands.

MEASUREMENTS

All participants were subjected to biochemical and body imaging examinations for a complete assessment of the extent and spread of disease. Clinical data obtained this way were further analysed.

RESULTS

The mean age of this cohort was 44.5 ± 17.4 years, and more than half carried the same founder SDHB mutation. About 50.8% of the mutation carriers developed pheochromocytomas or paragangliomas. Compared to patients diagnosed through genetic screening, those diagnosed clinically were characterized by larger tumours (P < .001), more frequent metastases (P = .024), were more frequently subjected to surgery (P = .011) and radiotherapy (P = .013), and had worse outcomes, such as macroscopic positive margins (P = .034). Persistent and/or unresectable disease and disease-related mortality were also more frequent in symptomatic patients compared to those diagnosed through genetic screening (P = .014).

CONCLUSIONS

In this nationwide cohort study, a large proportion of mutation carriers were found to develop SDHx-related neoplasia. Genetic testing and subsequent follow-up resulted in the diagnosis of smaller and nonmetastatic tumours, fewer treatment procedures, fewer complications and greater number of disease-free patients.

Identification of a novel SDHB c.563 T > C mutation responsible for Paraganglioma syndrome and genetic analysis of the SDHB gene in China: a case report

BACKGROUND

Pheochromocytoma/paraganglioma (PPGL) is a rare neuroendocrine tumor. Succinate dehydrogenase (SDH) deficiency has been confirmed to be associated with PPGL in various studies. SDHB mutations play an important role in PPGL. However, genetic screening of PPGL patients has not been widely carried out in clinics in China, and only a few related studies have been reported.

CASE PRESENTATION

We report a case of a 23-year-old woman with paraganglioma (PGL) caused by a novel missense SDHB mutation, c.563 T > C (p.Leu188Pro), who presented with paroxysmal hypertension. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a PGL in the right retroperitoneum and no metastasis. The patient was treated with surgical excision and did not have postsurgerical paroxysmal hypertension. In addition, we searched the literature related to variations in SDHB genes in Chinese patients with PPGL using multiple online databases, including PubMed, China Hospital Knowledge Database and Wanfang Data. Ultimately, 14 studies (published between 2006 and 2019) comprising 34 cases of SDHB-related PGL or pheochromocytoma (PCC) were found. In total, 35 patients were enrolled in this study, and 25 mutations were identified. The common genetic alterations of SDHB in China were c.136C > T (11.4%), c.18C > A (11.4%) and c.725G > A (8.5%). Some carriers of SDHB mutations (28.1%) developed metastatic PPGL, and a high frequency of head and neck PGLs (HNPGLs) (59.4%) was reported.

CONCLUSIONS

We describe a classic case with a novel SDHB c.563 T > C mutation. Based on our literature review, common SDHB gene mutations in Chinese PPGL patients are c.136C > T, c.18C > A and c.725G > A.

Imaging Features of Succinate Dehydrogenase-deficient Pheochromocytoma-Paraganglioma Syndromes

Pheochromocytoma (PC) and paraganglioma (PGL) are rare neuroendocrine tumors that occur throughout the body from the base of the skull to the pelvis. Sympathetic catecholamine-secreting tumors may be associated with hyperadrenergic symptoms and long-term morbidity if they are untreated. Typically biochemically silent, head and neck PGLs may result in cranial nerve palsies and symptoms due to localized mass effect. Tumors can arise sporadically or as part of an inheritable PC-PGL syndrome. Up to 40% of tumors are recognized to be associated with germline mutations in an increasing array of susceptibility genes, including those that appear to arise sporadically. Most commonly, up to 25% of all PC-PGLs are associated with mutations in one of the succinate dehydrogenase (SDH) enzyme subunit genes. The resulting familial PC-PGL syndrome varies according to the affected enzyme subunit (most commonly SDHB and SDHD mutations) with respect to tumor prevalence, location, age of onset, and risk of malignancy. Patients with SDH enzyme mutations have increased lifetime risk of developing multifocal tumors and malignancy. Early recognition of individuals at high risk, genetic testing, screening of family members, and lifelong surveillance programs are recommended, but not without health, economic, and psychologic implications. Anatomic and functional imaging is key to diagnosis, staging, treatment planning, and lifelong surveillance of these individuals. Radiologists must be aware of the imaging appearance of these varied tumors.^©RSNA, 2019.

Pheochromocytoma and Paraganglioma in Children and Adolescents: Experience of the French Society of Pediatric Oncology (SFCE)

Purpose

The purpose of this work is to assess the clinical outcome of pediatric patients diagnosed with pheochromocytoma and paraganglioma (PPGL) detected in France since 2000.

Methods

A retrospective multicenter study was conducted that included all patients younger than 18 years with PPGL diagnosed in France between 2000 and 2016. Patients were identified from 4 different sources: the National Registry of Childhood Solid Tumors, the French Pediatric Rare Tumors Database, the French registry of succinate dehydrogenase (SDH)-related hereditary paraganglioma, and the nationwide TenGen network.

Results

Among 113 eligible patients, 81 children with available data were enrolled (41 with adrenal and 40 with extra-adrenal PPGL). At diagnosis, 11 had synchronous metastases. After a median follow-up of 53 months, 27 patients experienced a new event (n = 7 second PPGL, n = 1 second paraganglioma [PGL], n = 8 local recurrences, n = 10 metastatic relapses, n = 1 new tumor) and 2 patients died of their disease. The 3- and 10-year event-free survival rates were 80% (71%-90%) and 39% (20%-57%),respectively, whereas the overall survival rate was 97% (93%-100%)at 3 and 10 years. A germline mutation in one PPGL-susceptibility gene was identified in 53 of the 68 (77%) patients who underwent genetic testing (SDHB [n = 25], VHL [n = 21], RET [n = 2], HIF2A [n = 2], SDHC [n = 1], SDHD [n = 1], NF1 [n = 1]). Incomplete resection and synchronous metastases were associated with higher risk of events (P = .011, P = .004), but presence of a germline mutation was not (P = .11).

Conclusions

Most pediatric PPGLs are associated with germline mutations and require specific follow-up because of the high risk of tumor recurrence.

An overview of 20 years of genetic studies in pheochromocytoma and paraganglioma

Paragangliomas and pheochromocytomas (PPGL) are rare neuroendocrine tumours characterized by a strong genetic determinism. Over the past 20 years, evolution of PPGL genetics has revealed that around 40% of PPGL are genetically determined, secondary to a germline mutation in one of more than twenty susceptibility genes reported so far. More than half of the mutations occur in one of the SDHx genes (SDHA, SDHB, SDHC, SDHD, SDHAF2), which encode the different subunits and assembly protein of a mitochondrial enzyme, succinate dehydrogenase. These susceptibility genes predispose to early forms (VHL, RET, SDHD, EPAS1, DLST), syndromic (RET, VHL, EPAS1, NF1, FH), multiple (SDHD, TMEM127, MAX, DLST, MDH2, GOT2) or malignant (SDHB, FH, SLC25A11) PPGL. The discovery of a germline mutation in one of these genes changes the patient's follow-up and allows genetic screening of affected families and the presymptomatic follow-up of relatives carrying a mutation.

Current management of succinate dehydrogenase-deficient gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are increasingly recognized as having diverse biology. With the development of tyrosine kinase inhibitors molecularly matched to oncogenic KIT and PDGFRA mutations, GISTs have become a quintessential model for precision oncology. However, about 5-10% of GIST lack these driver mutations and are deficient in succinate dehydrogenase (SDH), an enzyme that converts succinate to fumarate. SDH deficiency leads to accumulation of succinate, an oncometabolite that promotes tumorigenesis. SDH-deficient GISTs are clinically unique in that they generally affect younger patients and are associated with GIST-paraganglioma hereditary syndrome, also known as Carney-Stratakis Syndrome. SDH-deficient GISTs are generally resistant to tyrosine-kinase inhibitors, the standard treatment for advanced or metastatic GIST. Thus, surgical resection is the mainstay of treatment for localized disease, but recurrence is common. Clinical trials are currently underway investigating systemic agents for treatment of advanced SDH-deficient GIST. However, further studies are warranted to improve our understanding of SDH-deficient GIST disease biology, natural history, surgical approaches, and novel therapeutics.

Risk of metastatic pheochromocytoma and paraganglioma in SDHx mutation carriers: a systematic review and updated meta-analysis

BACKGROUND

Pheochromocytoma and paraganglioma (PPGL) are tumours that arise from chromaffin cells. Some genetic mutations influence PPGL, among which, those in genes encoding subunits of succinate dehydrogenase (SDHA, SDHB, SDHC and SDHD) and assembly factor (SDHAF2) are the most relevant. However, the risk of metastasis posed by these mutations is not reported except for SDHB and SDHD mutations. This study aimed to update the metastatic risks, considering prevalence and incidence of each SDHx mutation, which were dealt formerly all together.

METHODS

We searched EMBASE and MEDLINE and selected 27 articles. The patients included in the studies were divided into three groups depending on the presence of PPGL. We checked the heterogeneity between studies and performed a meta-analysis using Hartung-Knapp-Sidik-Jonkman method based on a random effect model.

RESULTS

The highest PPGL prevalence was for SDHB mutation, ranging from 23% to 31%, and for SDHC mutation (23%), followed by that for SDHA mutation (16%). The lowest prevalence was for SDHD mutation, ranging from 6% to 8%. SDHAF2 mutation showed no metastatic events. The PPGL incidence showed a tendency similar to that of its prevalence with the highest risk of metastasis posed by SDHB mutation (12%-41%) and the lowest risk by SDHD mutation (~4%).

CONCLUSION

There was no integrated evidence of how SDHx mutations are related to metastatic PPGL. However, these findings suggest that SDHA, SDHB and SDHC mutations are highly associated and should be tested as indicators of metastasis in patients with PPGL.

Diffusion-weighted imaging (DWI) highlights SDHB-related tumours: A pilot study

OBJECTIVE

There is consensus that asymptomatic carriers of SDHB mutations should undergo periodic surveillance imaging. MRI has the advantage of avoiding radiation exposure but its sensitivity and specificity for detecting phaeochromocytoma and paraganglioma (PPGL) are dependent on sequences performed and expertise of reporting radiologists. We aim to highlight the additional value of diffusion-weighted imaging (DWI) for MR based surveillance, demonstrating DWI's ability to identify small PPGLs at all body sites.

DESIGN

We presented DWI sequences taken as part of SDHB surveillance to a radiologist, expert in reporting PPGL screening scans. Areas of high signal on DWI were interrogated using other standard MRI sequences.

PATIENTS

We reviewed the MRI scans for 18 SDHB mutation carriers with a total of 18 histologically proven SDHB-related tumours and 12 presumed PGLs/metastatic deposits.

RESULTS

The DWI sequences identified all 30 lesions. False-positive lesions were excluded by standard sequences. The tumours detected by DWI ranged in size from 5 to 52 mm. PPGLs were identified on DWI in the abdomen (n = 14), adrenal gland (n = 1), thorax (n = 3), neck (n = 2) and bladder (n = 2). Additionally, other SDHB-related tumours (GIST, RCC) were also highlighted by DWI, as were metastatic deposits in the liver and bone.

CONCLUSIONS

These preliminary data suggest that DWI has high sensitivity and can identify even small SDHB-related tumours. If these findings are confirmed in larger series, for all SDH subunits, it will provide reassurance about identifying small SDH-related tumours, without exposing patients to the consequences of radiation-based imaging and will secure the role of MRI for surveillance imaging.

Precision Surgery for Pheochromocytomas and Paragangliomas

Since Felix Fränkel's account of pheochromocytoma in 1886, great discoveries and vast advancements in the diagnosis, genetics, anatomical and functional imaging techniques, and surgical management of pheochromcytoma and paraganglioma (P-PGL) have been made. The improved insight in the pathophysiology of P-PGL and more accurate detection methods enable physicians to tailor the treatment plan to an individual based on the genetic profile and tumor behavior. This review will cover briefly the clinical features, diagnosis, genetic mutations, and imaging modalities that are used to guide current surgical management of these rare and interesting endocrinopathies.

Clinical Practice Guidance: Surveillance for phaeochromocytoma and paraganglioma in paediatric succinate dehydrogenase gene mutation carriers

The succinate dehydrogenase (SDH) enzyme complex functions as a key enzyme coupling the oxidation of succinate to fumarate in the citric acid cycle. Inactivation of this enzyme complex results in the cellular accumulation of the oncometabolite succinate, which is postulated to be a key driver in tumorigenesis. Succinate accumulation inhibits 2-oxoglutarate-dependent dioxygenases, including DNA and histone demethylase enzymes and hypoxic gene response regulators. Biallelic inactivation (typically resulting from one inherited and one somatic event) at one of the four genes encoding the SDH complex (SDHA/B/C/D) is the most common cause for SDH deficient (dSDH) tumours. Germline mutations in the SDHx genes predispose to a spectrum of tumours including phaeochromocytoma and paraganglioma (PPGL), wild type gastrointestinal stromal tumours (wtGIST) and, less commonly, renal cell carcinoma and pituitary tumours. Furthermore, mutations in the SDHx genes, particularly SDHB, predispose to a higher risk of malignant PPGL, which is associated with a 5-year mortality of 50%. There is general agreement that biochemical and imaging surveillance should be offered to asymptomatic carriers of SDHx gene mutations in the expectation that this will reduce the morbidity and mortality associated with dSDH tumours. However, there is no consensus on when and how surveillance should be performed in children and young adults. Here, we address the question: "What age should clinical, biochemical and radiological surveillance for PPGL be initiated in paediatric SDHx mutation carriers?".

Positive Impact of Genetic Test on the Management and Outcome of Patients With Paraganglioma and/or Pheochromocytoma

CONTEXT

Pheochromocytomas and paragangliomas (PPGLs) are characterized by a strong genetic component, with up to 40% of patients carrying a germline mutation in a PPGL susceptibility gene. International guidelines recommend that genetic screening be proposed to all patients with PPGL.

OBJECTIVE

Our objective was to evaluate how a positive genetic test impacts the management and outcome of patients with SDHx or VHL-related PPGL.

DESIGN

We performed a multicentric retrospective study involving 221 propositi carrying an SDHB, SDHD, SDHC, or VHL germline mutation. Patients were divided into two groups: genetic patients, who were informed of their genetic status within the year following the first PPGL diagnosis, and historic patients, who only benefited from the genetic test several years after initial PPGL diagnosis.

RESULTS

Genetic patients had better follow-up than historic patients, with a greater number of examinations and a reduced number of patients lost to follow-up (9.6% vs 72%, respectively). During follow-up, smaller (18.7 vs 27.6 mm; P = 0.0128) new PPGLs and metastases as well as lower metastatic spread were observed in genetic patients. Of note, these differences were reversed in the historic cohort after genetic testing. Genetic patients who developed metachronous metastases had a better 5-year survival rate than historic patients (P = 0.0127).

CONCLUSION

Altogether, our data suggest that early knowledge of genetic status had a positive impact on the management and clinical outcome of patients with a germline SDHx or VHL mutation.

An analysis of surveillance screening for SDHB-related disease in childhood and adolescence

Objective Phaeochromocytomas (PCC) and paragangliomas (PGL) are rare in children. A large proportion of these are now understood to be due to underlying germline mutations. Here we focus on succinate dehydrogenase subunit B (SDHB) gene mutation carriers as these tumours carry a high risk of malignant transformation. There remains no current consensus with respect to optimal surveillance for asymptomatic carriers and those in whom the presenting tumour has been resected. Method We undertook a retrospective analysis of longitudinal clinical data of all children and adolescents with SDHB mutations followed up in a single UK tertiary referral centre. This included index cases that pre-dated the introduction of surveillance screening and asymptomatic carriers identified through cascade genetic testing. We also conducted a literature review to inform a suggested surveillance protocol for children and adolescents harbouring SDHB mutations. Results Clinical outcomes of a total of 38 children are presented: 8 index cases and 30 mutation-positive asymptomatic carriers with 175 patient years of follow-up data. Three of the eight index cases developed metachronous disease and two developed metastatic disease. Of the 30 asymptomatic carriers, 3 were found to have PGLs on surveillance screening. Conclusions Surveillance screening was well tolerated in our paediatric cohort and asymptomatic paediatric subjects. Screening can identify tumours before they become secretory and/or symptomatic, thereby facilitating surgical resection and reducing the chance of distant spread. We propose a regular screening protocol commencing at age 5 years in this at-risk cohort of patients.

Can subunit-specific phenotypes guide surveillance imaging decisions in asymptomatic SDH mutation carriers?

OBJECTIVE

With the discovery that familial phaeochromocytoma and paraganglioma syndrome can be caused by mutations in each subunit of the succinate dehydrogenase enzyme (SDH), has come the recognition that mutations in the individual subunits have their own distinct natural histories. Increased genetic screening is leading to the identification of increasing numbers of, mostly asymptomatic, gene mutation carriers and the implementation of screening strategies for these individuals. Yet there is, to date, no international consensus regarding screening strategies for asymptomatic carriers.

DESIGN

A comprehensive PubMed search from 1/1/2000 to 28/2/2018 was undertaken using multiple search terms and subsequently a manual review of references in identified papers to identify all clinically relevant cases and cohorts. In this review, the accumulated, published experience of phenotype and malignancy risks of individual SDH subunits is analysed. Where possible screening results for asymptomatic SDH mutation carriers have been analysed separately to define the penetrance in asymptomatic carriers (asymptomatic penetrance).

RESULTS

The combined data confirms that "asymptomatic penetrance" is highest for SDHD and when there is penetrance, the most likely site to develop a PGL is head and neck (SDHD) and extra-adrenal abdominal (SDHB). However, the risk in SDHB carriers of developing HNPGL is also high (35.5%) and a PCC is low (15.1%), and in SDHD carriers there is a high risk of developing a PCC (35.8%) or abdominal PGL (9.4%) and a small, but significant risk at other sympathetic sites. The data suggest that the risk of malignant transformation is the same for both PCC and extra-adrenal abdominal PGLs (30%-35%) in SDHB carriers. In SDHD carriers, the risk of malignant transformation was highest in HNPGLs (7.5%) and similar for sympathetic sites (3.8%-5.2%).

CONCLUSIONS

Using this data, we suggest surveillance screening of asymptomatic carriers can be tailored to the underlying SDH subunit and review possible surveillance programmes.

Succinate dehydrogenase mutations: paraganglioma imaging and at-risk population screening

Paragangliomas are rare vascular tumours of the autonomic nervous system. They can be classified as sympathetic or parasympathetic. Sympathetic paragangliomas, which include phaeochromocytomas, tend to be functional and symptomatic. Parasympathetic paragangliomas are usually non-functional and may present with mass effect. Forty percent of paragangliomas are linked to genetic syndromes, most commonly due to mutations of the succinate dehydrogenase (SDH) enzyme complex and are collectively known as paraganglioma syndromes, of which five are described. Genetic testing is recommended for all patients, and their first-degree relatives, diagnosed with paragangliomas. When SDH mutations are discovered, biochemical screening and imaging surveillance is indicated. There is currently no consensus on imaging surveillance protocols. Most advocate full-body imaging, but the choice of technique and frequency varies. If paragangliomas are demonstrated, functional imaging to look for synchronous tumours or metastases is indicated. 2-[¹⁸F]-fluoro-2-deoxy-d-glucose (¹⁸F-FDG) positron-emission tomography (PET)-computed tomography (CT) is the technique of choice for metastatic evaluation, but [¹²³I]-metaiodobenzylguanidine or [¹¹¹In]-DTPA-octreotide scintigraphy are also utilised. Current research into emerging positron-emitting radiolabelled somatostatin analogues have yielded promising results, which is likely to be reflected in future guidelines. As genetic testing becomes increasingly prevalent, the need to answer the remaining questions regarding surveillance imaging is paramount.

[Hereditary pheochromocytoma and paraganglioma: screening and follow-up strategies in asymptomatic mutation carriers]

The management of pheochromocytoma and paraganglioma has deeply evolved over the last years due to the discovery of novel genes of susceptibility, especially SDHx, MAX and TMEM127. While the modalities of diagnosis and management of patients presenting with hereditary pheochromocytoma and paraganglioma are now well defined, screening and follow-up strategies for asymptomatic mutation carriers remain a matter of debate. This raises major questions as these asymptomatic patients will require a lifelong follow-up. The aim of this review is an attempt to give insights on the optimal screening and follow-up strategies of asymptomatic carriers of SDHx, MAX and TMEM127 mutations, with additional thoughts on the forensic and psychological aspects of the management of such patients with rare diseases.

A patient with a germline SDHB mutation presenting with an isolated pituitary macroprolactinoma

Symptomatic pituitary adenomas occur with a prevalence of approximately 0.1% in the general population. It is estimated that 5% of pituitary adenomas occur in a familial setting, either in isolated or syndromic form. Recently, loss-of-function mutations in genes encoding succinate dehydrogenase subunits (SDHx) or MYC-associated factor X (MAX) have been found to predispose to pituitary adenomas in co-existence with paragangliomas or phaeochromocytomas. It is rare, however, for a familial SDHx mutation to manifest as an isolated pituitary adenoma. We present the case of a pituitary lactotroph adenoma in a patient with a heterozygous germline SDHB mutation, in the absence of concomitant neoplasms. Initially, the adenoma showed biochemical response but poor tumour shrinkage in response to cabergoline; therefore, transsphenoidal surgery was performed. Following initial clinical improvement, tumour recurrence was identified 15 months later. Interestingly, re-initiation of cabergoline proved successful and the lesion demonstrated both biochemical response and tumour shrinkage. Our patient’s SDHB mutation was identified when we realised that her father had a metastatic paraganglioma, prompting genetic testing. Re-inspection of the histopathological report of the prolactinoma confirmed cells with vacuolated cytoplasm. This histological feature is suggestive of an SDHx mutation and should prompt further screening for mutations by immunohistochemistry and/or genetic testing. Surprisingly, immunohistochemistry of this pituitary adenoma demonstrated normal SDHB expression, despite loss of SDHB expression in the patient’s father’s paraganglioma.

Advances in adrenal tumors 2018

This review aims to provide clinicians and researchers with a condensed update on the most important studies in the field during 2017. We present the academic output measured by active clinical trials and peer-reviewed published manuscripts. The most important and contributory manuscripts were summarized for each diagnostic entity, with a particular focus on manuscripts that describe translational research that have the potential to improve clinical care. Finally, we highlight the importance of collaborations in adrenal tumor research, which allowed for these recent advances and provide structures for future success in this scientific field.

Tumour risks and genotype-phenotype correlations associated with germline variants in succinate dehydrogenase subunit genes SDHB, SDHC and SDHD

BACKGROUND

Germline pathogenic variants in SDHB/SDHC/SDHD are the most frequent causes of inherited phaeochromocytomas/paragangliomas. Insufficient information regarding penetrance and phenotypic variability hinders optimum management of mutation carriers. We estimate penetrance for symptomatic tumours and elucidate genotype-phenotype correlations in a large cohort of SDHB/SDHC/SDHD mutation carriers.

METHODS

A retrospective survey of 1832 individuals referred for genetic testing due to a personal or family history of phaeochromocytoma/paraganglioma. 876 patients (401 previously reported) had a germline mutation in SDHB/SDHC/SDHD (n=673/43/160). Tumour risks were correlated with in silico structural prediction analyses.

RESULTS

Tumour risks analysis provided novel penetrance estimates and genotype-phenotype correlations. In addition to tumour type susceptibility differences for individual genes, we confirmed that the SDHD:p.Pro81Leu mutation has a distinct phenotype and identified increased age-related tumour risks with highly destabilising SDHB missense mutations. By Kaplan-Meier analysis, the penetrance (cumulative risk of clinically apparent tumours) in SDHB and (paternally inherited) SDHD mutation-positive non-probands (n=371/67 with detailed clinical information) by age 60 years was 21.8% (95% CI 15.2% to 27.9%) and 43.2% (95% CI 25.4% to 56.7%), respectively. Risk of malignant disease at age 60 years in non-proband SDHB mutation carriers was 4.2%(95% CI 1.1% to 7.2%). With retrospective cohort analysis to adjust for ascertainment, cumulative tumour risks for SDHB mutation carriers at ages 60 years and 80 years were 23.9% (95% CI 20.9% to 27.4%) and 30.6% (95% CI 26.8% to 34.7%).

CONCLUSIONS

Overall risks of clinically apparent tumours for SDHB mutation carriers are substantially lower than initially estimated and will improve counselling of affected families. Specific genotype-tumour risk associations provides a basis for novel investigative strategies into succinate dehydrogenase-related mechanisms of tumourigenesis and the development of personalised management for SDHB/SDHC/SDHD mutation carriers.

Extent of surgery for phaeochromocytomas in the genomic era

Background

Germline mutations are present in 20–30 per cent of patients with phaeochromocytoma. For patients who develop bilateral disease, complete removal of both adrenal glands (total adrenalectomy) will result in lifelong adrenal insufficiency with an increased risk of death from adrenal crisis. Unilateral/bilateral adrenal-sparing surgery (subtotal adrenalectomy) offers preservation of cortical function and independence from steroids, but leaves the adrenal medulla in situ and thus at risk of developing new and possibly malignant disease. Here, present knowledge about how tumour genotype relates to clinical behaviour is reviewed, and application of this knowledge when choosing the extent of adrenalectomy is discussed.

Methods

A literature review was undertaken of the penetrance of the different genotypes in phaeochromocytomas, the frequency of bilateral disease and malignancy, and the underlying pathophysiological mechanisms, with emphasis on explaining the clinical phenotypes of phaeochromocytomas and their associated syndromes.

Results

Patients with bilateral phaeochromocytomas most often have multiple endocrine neoplasia type 2 (MEN2) or von Hippel–Lindau disease (VHL) with high-penetrance mutations for benign disease, whereas patients with mutations in the genes encoding SDHB (succinate dehydrogenase subunit B) or MAX (myelocytomatosis viral proto-oncogene homologue-associated factor X) are at increased risk of malignancy.

Conclusion

Adrenal-sparing surgery should be the standard approach for patients who have already been diagnosed with MEN2 or VHL when operating on the first side, whereas complete removal of the affected adrenal gland(s) is generally recommended for patients with SDHB or MAX germline mutations. Routine assessment of a patient's genotype, even after the first operation, can be crucial for adopting an appropriate strategy for follow-up and future surgery.

European Society of Endocrinology Clinical Practice Guidelines for the management of aggressive pituitary tumours and carcinomas

BACKGROUND

Pituitary tumours are common and easily treated by surgery or medical treatment in most cases. However, a small subset of pituitary tumours does not respond to standard medical treatment and presents with multiple local recurrences (aggressive pituitary tumours) and in rare occasion with metastases (pituitary carcinoma). The present European Society of Endocrinology (ESE) guideline aims to provide clinical guidance on diagnosis, treatment and follow-up in aggressive pituitary tumours and carcinomas.

METHODS

We decided upfront, while acknowledging that literature on aggressive pituitary tumours and carcinomas is scarce, to systematically review the literature according to the GRADE (Grading of Recommendations Assessment, Development and Evaluation) system. The review focused primarily on first- and second-line treatment in aggressive pituitary tumours and carcinomas. We included 14 single-arm cohort studies (total number of patients = 116) most on temozolomide treatment (n = 11 studies, total number of patients = 106). A positive treatment effect was seen in 47% (95% CI: 36-58%) of temozolomide treated. Data from the recently performed ESE survey on aggressive pituitary tumours and carcinomas (165 patients) were also used as backbone for the guideline. SELECTED RECOMMENDATION: (i) Patients with aggressive pituitary tumours should be managed by a multidisciplinary expert team. (ii) Histopathological analyses including pituitary hormones and proliferative markers are needed for correct tumour classification. (iii) Temozolomide monotherapy is the first-line chemotherapy for aggressive pituitary tumours and pituitary carcinomas after failure of standard therapies; treatment evaluation after 3 cycles allows identification of responder and non-responder patients. (iv) In patients responding to first-line temozolomide, we suggest continuing treatment for at least 6 months in total. Furthermore, the guideline offers recommendations for patients who recurred after temozolomide treatment, for those who did not respond to temozolomide and for patients with systemic metastasis.

When should genetic testing be performed in patients with neuroendocrine tumours?

Neuroendocrine tumours (NETs) are a heterogenous group of tumours arising from neuroendocrine cells in several sites around the body. They include tumours of the gastroenteropancreatic system, phaeochromocytoma and paraganglioma and medullary thyroid cancer. In recent years, it has become increasingly apparent that a number of these tumours arise as a result of germline genetic mutations and are inherited in an autosomal dominant pattern. The number of genes implicated is increasing rapidly. Identifying which patients are likely to have a germline mutation enables clinicians to counsel patients adequately about their future disease risk, and allows for earlier detection of at-risk patients through family screening. The institution of screening and surveillance programmes may in turn lead to a major shift in presentation patterns for some of these tumours. In this review, we examine the features which may lead a clinician to suspect that a patient may have an inherited cause of a NET and we outline which underlying conditions should be suspected. We also discuss what type of screening may be appropriate in a variety of situations.

Radiological Surveillance Screening in Asymptomatic Succinate Dehydrogenase Mutation Carriers

There has been a significant increase in the availability of testing for pheochromocytoma and paraganglioma (PPGL) germline susceptibility genes. As more patients with genetic mutations are identified, cascade genetic testing of family members is also increasing. This results in identifying genetic predispositions at a much earlier age. With our current understanding of familial PPGL syndromes, lifelong surveillance is required. This review focuses on carriers of succinate dehydrogenase (SDH) mutations. For genetic testing to be proven worthwhile, the results must be used for patient benefit. For SDHx mutations, this should equate to a surveillance program that is safe and removes as much uncertainty around diagnosis as possible. Early identification of these tumors is the goal of any surveillance program, as surgical resection is the mainstay of treatment with curative intent to prevent the morbidity and mortality consequences associated with catecholamine excess, in addition to the risk of malignancy. Modality and frequency of surveillance imaging and how to engage individuals in the process of surveillance remain controversial questions. The data reviewed here and the cumulative advice supports the avoidance of using radiation-exposing imaging in this group of individuals that require lifelong screening.