Pheochromocytomas And Paragangliomas Research Articles

Targeting Left Ventricular Mechanics In Patients With Pheochromocytoma/Paraganglioma: An Updated Meta-analysis.

Numerous studies targeting left ventricular (LV) systolic function by measuring LV ejection fraction (LVEF) in patients with pheochromocytoma and paraganglioma (PPGL) either failed to reveal any impairment of this parameter or found a super-normal systolic function compared to essential hypertensives or normotensive controls. To provide an updated piece of information on LV systolic dysfunction in the PPGL setting, we performed a meta-analysis of speckle tracking echocardiography (STE) studies investigating LV mechanics via global longitudinal strain (GLS), a more sensitive index of LV systolic function than LVEF. A computerized search was performed using PubMed, OVID, EMBASE, and Cochrane library databases from inception until September 30, 2022. Full articles reporting data on LV GLS and LVEF in patients with PPGL and controls were considered suitable. A total of 252 patients with PPGL and 187 controls were included in 6 studies. LV GLS was worse in the pooled PPGL group than in the control group (-17.3 ± 1.2 vs. -20.0 ± 0.6) with a standard means difference (SMD) of 1.13 ± 0.36 confidence interval (CI: 0.43-1.84, P = 0.002), whereas this was not the case for LVEF (67.3 ± 1.9 and 66.4 ± 1.6%, respectively), SMD: 0.12 ± 0.03, (CI: -0.41/0.65, P = 0.66). A meta-regression analysis in PPGL patients showed an inverse relationship between adrenergic activity and GLS (P < 0.0001). Our findings suggest that early changes in LV systolic function not detectable by conventional echocardiography in the PPGL setting can be revealed by STE; therefore, STE implementation in the workup of patients with PPGL may improve the detection of subclinical systolic dysfunction.

The clinical utility of plasma and urine metanephrines in hypertensive emergency.

Metanephrines (MTNs) are metabolites of catecholamines and are constantly produced in high amounts by pheochromocytomas and paragangliomas (PPGLs). Marked MTN elevations (> 3 times the upper limit of normal [ULN]) are highly suggestive of PPGL. The frequency of marked MTN elevations in non-PPGL hypertensive emergencies (HTNEs) is unknown. We retrospectively analyzed plasma free metanephrine (PMTN) and 24-h urinary fractionated metanephrine (UMTN) levels in 48 consecutive patients (59.7 ± 15.6years; 48% female; BMI: 31 ± 9.7kg/m2) hospitalized for HTNE, defined as systolic blood pressure (SBP) > 180mmHg or diastolic blood pressure (DBP) > 120mmHg with end-organ damage. PMTNs were measured in 47 patients, UMTNs were measured in 16 patients, and both PMTNs and UMTNs were measured in 15 patients. PMTN/UMTN levels were not associated with SBP/DBP, comorbidities, end-organ damage, or interfering medications, the exception being that plasma normetanephrines (PNMNs) were significantly associated with comorbidities (Adj. R2 = 0.16; p = 0.04) and interfering medications (Adj. R2 = 0.15; p = 0.03), although with weak correlation. Marked MTN (specifically PNMN) elevations (647, 521, and 453pg/mL; normal ≤ 148pg/mL) were noted in only three patients (6%). Marked MTN elevations in HTNE are uncommon. Therefore, we recommend against measuring MTN in the setting of an apparent precipitating cause of HTNE to avoid unnecessary testing and imaging. Testing for MTN in HTNE should be pursued only when there is no clear precipitating cause and in cases where there is strong underlying clinical suspicion for PPGL. However, should testing be performed, marked MTN elevations should not be disregarded as being a commonly occurring result of HTNE.

PS-C22-5: PLASMA METANEPHRINES PROVIDE GREATER SPECIFICITY THAN URINARY METANEPHRINES IN PATIENTS WITH OBSTRUCTIVE SLEEP APNEA: A PROSPECTIVE TRIAL

Introduction: Pheochromocytoma and paraganglioma (PPGL), and obstructive sleep apnea (OSA) are important secondary causes of hypertension. Both plasma and urinary metanephrines have high diagnostic sensitivity and specificity for diagnosis of PPGL. Patients with OSA have increased nocturnal catecholamine release, which can lead to increased metanephrines production over 24 hours. We hypothesized that morning plasma metanephrines have a higher diagnostic accuracy than 24-hour urinary metanephrines in patients with OSA. Methods: We recruited patients undergoing polysomnography for suspected OSA. Plasma and 24-hour urinary metanephrines were measured. Patients with elevated metanephrines had repeated measurements of metanephrines, imaging and follow-up, to diagnose, or exclude, PPGL. Results: Seventy-six patients completed polysomnography and biochemical testing, of which 68 had OSA. One patient had a PPGL, while PPGL was excluded in the remaining patients. At baseline, OSA patients were more likely to have falsely-elevated urinary (17 of 67, 25.4%), than falsely-elevated plasma metanephrines (2 of 67, 2.9%) (P &lt; 0.01). Seven patients had normal metanephrines on repeat testing. Nine patients with persistently elevated metanephrines underwent abdominal imaging: six patients had no PPGL, one had lipid-rich adrenal adenomas, one had indeterminate adrenal adenoma, and one had bladder tumor. This final patient with biopsy-proven bladder PPGL had marginally-elevated urinary metanephrines, but false-negative plasma metanephrines, due to the small tumor size. Falsely-elevated urine metanephrines were more common in patients with severe OSA (13 of 3, 38.2%), compared to moderate OSA (1 of 13, 7.7%) and mild OSA (3 of 20, 15%), P &lt; 0.01. Falsely-elevated plasma and urine metanephrines were all due to elevation of normetanephrine, while metanephrine was normal in all patients. Declines in metanephrines were observed only in patients with OSA treated with continuous positive pressure ventilation, while those untreated had no improvements. Conclusion: In patients with OSA, metanephrines measured in plasma provide better specificity than those measured in urine for the diagnosis of PPGL. However, one patient with a small PPGL was missed by plasma metanephrines.

Pheochromocytoma: a changing perspective and current concepts

This article aims to review current concepts in diagnosing and managing pheochromocytoma and paraganglioma (PPGL). Personalized genetic testing is vital, as 40–60% of tumors are linked to a known mutation. Tumor DNA should be sampled first. Next-generation sequencing is the best and most cost-effective choice and also helps with the expansion of current knowledge. Recent advancements have also led to the increased incorporation of regulatory RNA, metabolome markers, and the NETest in PPGL workup. PPGL presentation is highly volatile and nonspecific due to its multifactorial etiology. Symptoms mainly derive from catecholamine (CMN) excess or mass effect, primarily affecting the cardiovascular system. However, paroxysmal nature, hypertension, and the classic triad are no longer perceived as telltale signs. Identifying high-risk subjects and diagnosing patients at the correct time by using appropriate personalized methods are essential. Free plasma/urine catecholamine metabolites must be first-line examinations using liquid chromatography with tandem mass spectrometry as the gold standard analytical method. Reference intervals should be personalized according to demographics and comorbidity. The same applies to result interpretation. Threefold increase from the upper limit is highly suggestive of PPGL. Computed tomography (CT) is preferred for pheochromocytoma due to better cost-effectiveness and spatial resolution. Unenhanced attenuation of &gt;10HU in non-contrast CT is indicative. The choice of extra-adrenal tumor imaging is based on location. Functional imaging with positron emission tomography/computed tomography and radionuclide administration improves diagnostic accuracy, especially in extra-adrenal/malignant or familial cases. Surgery is the mainstay treatment when feasible. Preoperative α-adrenergic blockade reduces surgical morbidity. Aggressive metastatic PPGL benefits from systemic chemotherapy, while milder cases can be managed with radionuclides. Short-term postoperative follow-up evaluates the adequacy of resection. Long-term follow-up assesses the risk of recurrence or metastasis. Asymptomatic carriers and their families can benefit from surveillance, with intervals depending on the specific gene mutation. Trials primarily focusing on targeted therapy and radionuclides are currently active. A multidisciplinary approach, correct timing, and personalization are key for successful PPGL management.

Nuclear and mitochondrial DNA alterations in pheochromocytomas and paragangliomas, and their potential treatment.

Mitochondrial DNA (mtDNA) alterations have been reported in different types of cancers and are suggested to play important roles in cancer development and metastasis. However, there is little information about its involvement in pheochromocytomas and paragangliomas (PCCs/PGLs) formation. PCCs and PGLs are rare endocrine tumors of the chromaffin cells in the adrenal medulla and extra-adrenal paraganglia that can synthesize and secrete catecholamines. Over the last 3 decades, the genetic background of about 60% of PCCs/PGLs involving nuclear DNA alterations has been determined. Recently, a study showed that mitochondrial alterations can be found in around 17% of the remaining PCCs/PGLs. In this review, we summarize recent knowledge regarding both nuclear and mitochondrial alterations and their involvement in PCCs/PGLs. We also provide brief insights into the genetics and the molecular pathways associated with PCCs/PGLs and potential therapeutical targets.

S-13-6: RECENT ADVANCES IN THE MANAGEMENT OF PHEOCHROMOCYTOMA AND PARAGANGLIOMA

Pheochromocytomas and paragangliomas (PPGL) are rare tumors that cause refractory hypertension and hypertensive crisis. Although metastatic disease accounts for 30% of PPGL, diagnosis of malignant is difficult without the presence of metastatic lesions. We review here several advancements in diagnosis and treatment of PPGL. A nationwide epidemiological survey in Japan revealed that the annual number of patients with PPGL was 3,000, higher than what was reported in previously. While plasma and urine fractionated metanephrines are recommended to be used as specific biochemical testing for diagnosis, creatinine-corrected fractionated metanephrines in spot urine samples which had been widely used in Japan as a convenient screening test was shown to be as useful as 24-hour urine fractionated metanephrines. Regarding imaging studies, a more specific functional imaging for PPGL, 68Ga DOTATATE, was newly developed. 68Ga DOTATATE provides a clear image with high sensitivity and specificity. Currently, PASS or GAPP histological scores and SDHB immunostaining are clinically used to attempt to discriminate benign from malignant tumor. However, since this distinguishing process remains difficult, all cases were classified as malignant with the possibility of metastasis in the WHO classification of endocrine tumor updated in 2017. Approximately 60% of PPGL have germline mutations of PPGL-related genes. Currently the genes are classified into 2 clusters based on their mechanism for etiology of tumorigenesis. Based on the possible mechanisms of tumor development associated with gene mutation, several molecular target drugs are under evaluation to explore more promising treatments for malignant PPGL.

Feohromocitom kao potencijalni uzrok napada epilepsije

Epileptic seizures are defined as the transient appearance of signs or symptoms due to excessive or synchronous neuronal activity in the cerebral cortex. Pheochromocytomas and paragangliomas (PPGL) are tumors of chromaffin cells that arise from the medulla of the adrenal gland in 80-85% of patients and from the extra-adrenal sympathetic tissue of the abdomen, pelvis and chest in 10-20% of patients. The clinical picture of PPGL is variable and ranges from the absence of symptoms to severe clinical picture, depending on the biochemical profile. They are most often manifested by paroxysmal hypertension, followed by episodes of severe headache or diaphoresis, while epileptic attacks are rare. Neurological symptoms are present in many patients with PPGL. Also, paroxysmal neurological conditions such as vasodilating headache, intracranial tumors, diencephalic-autonomic epilepsy, hypertensive encephalopathy, focal arterial disease of the brain and anxiety state have been described, which may have similar clinical manifestations with pheochromocytomas. We present a 44-year-old woman, who has been diagnosed with pheochromocytoma as possible etiological basis of epileptic seizures. Pheochromocytoma, with its low incidence and "chameleon" clinical spectrum, should be considered as a potential etiological factor of convulsions.

Epigenetic drugs in somatostatin type 2 receptor radionuclide theranostics and radiation transcriptomics in mouse pheochromocytoma models.

Pheochromocytomas and paragangliomas (PCCs/PGLs) are catecholamine-producing tumors. In inoperable and metastatic cases, somatostatin type 2 receptor (SSTR2) expression allows for peptide receptor radionuclide therapy with [177Lu]Lu-DOTA-TATE. Insufficient receptor levels, however, limit treatment efficacy. This study evaluates whether the epigenetic drugs valproic acid (VPA) and 5-Aza-2'-deoxycytidine (DAC) modulate SSTR2 levels and sensitivity to [177Lu]Lu-DOTA-TATE in two mouse PCC models (MPC and MTT). Methods: Drug-effects on Sstr2/SSTR2 were investigated in terms of promoter methylation, mRNA and protein levels, and radiotracer binding. Radiotracer uptake was measured in subcutaneous allografts in mice using PET and SPECT imaging. Tumor growth and gene expression (RNAseq) were characterized after drug treatments. Results: DAC alone and in combination with VPA increased SSTR2 levels along with radiotracer uptake in vitro in MPC (high-SSTR2) and MTT cells (low-SSTR2). MTT but not MPC allografts responded to DAC and VPA combination with significantly elevated radiotracer uptake, although activity concentrations remained far below those in MPC tumors. In both models, combination of DAC, VPA and [177Lu]Lu-DOTA-TATE was associated with additive effects on tumor growth delay and specific transcriptional responses in gene sets involved in cancer and treatment resistance. Effects of epigenetic drugs were unrelated to CpG island methylation of the Sstr2 promoter. Conclusion: This study demonstrates that SSTR2 induction in mouse pheochromocytoma models has some therapeutic benefit that occurs via yet unknown mechanisms. Transcriptional changes in tumor allografts associated with epigenetic treatment and [177Lu]Lu-DOTA-TATE provide first insights into genetic responses of PCCs/PGLs, potentially useful for developing additional strategies to prevent tumor recurrence.

PS-P10-7: SEVENTY YEARS OF PHEOCHROMOCYTOMAS AND PARAGANGLIOMAS IN ARGENTINA

In Argentina, data regarding Pheochromocytomas and Paragangliomas (PPGLs) are scarse. Objective: to describe demographic, biochemical and genetic characteristics of children and adults with confirmed PPGls. Design and method: Observational multicenter study of recruited participants surveyed from a retrospective cross sectional database from january 1953 until January 2022. Results: We included 486 patients (58.4% women) from 93 recruiting centers, mean age at diagnosis 38.3, 393 (80.9%) hypertensives, baseline office systolic/diastolic blood pressure 157.8/96.5 mmHg. Of all tumors, 382 (79.6%) were Pheochromocytomas, 67 (13.8%) paragangliomas and 11 (2.3%) mixed. The most prevalent cathecolamin secretion type was noradrenergic (35%), followed by adrenergic (30.6%) and mixed (20.3%). Local recurrence and mestastasis occured in 10% of subjects. The most common symptoms were headache (57%), sweating (57.5%) and palpitations (53.4%). In 147 patients with a genetic syndrome, we found 44 MEN2A, 7 MEN2B, 1 MEN1, 42 Von Hippel Lindau, 11 neurofibromatosis type 1, 32 PGL4, 6 PGL1, 2 MAX, 1 TMEM127, and 1 mosaic EPAS1/HIF2A. We found the genetic variant types in 102 patients. Conclusions: Our results are consistent with other publications from foreign databases. PPGls are rarely diagnosed in Argentina, and the genetic profile is lacking in three fourths of patients.

Genotype-Phenotype Correlations and Clinical Outcomes in 155 Cases of Pheochromocytoma and Paraganglioma.

Pheochromocytoma and paraganglioma (PPGL) are rare neuroendocrine tumours, often associated with germline mutations that influence the disease biology and clinical course. We aimed to describe the genotypic and phenotypic characteristics of a consecutive series of PPGL patients and correlate mutation status with clinical outcomes. We performed a retrospective cohort study of all PPGL patients who presented to a tertiary referral centre between March 2005 and February 2022. Genotypic, phenotypic and follow-up data were analysed. A total of 140 patients were included. Of these, 94 (67%) patients underwent genetic testing and a mutation was detected in 36 (38%) patients. Mutation presence was associated with younger age, smaller tumour size and bilateral adrenal tumours. Disease recurrence occurred at a median time of 5.4 (IQR 2.8-11.0) years after treatment in 21 (15%) patients, of which 14 (67%) had a mutation in a susceptibility gene. Recurrence pattern was influenced by mutation type; higher local recurrence risk for SDHA, SDHB, and MEN2B disease, and higher metastatic risk for SDHB, VHL and MEN2A disease. Recurrence occurred in three (3%) patients with mutation absence. Multivariate analysis revealed that age ≤40years and mutation presence were associated with increased risk of disease recurrence. Genotypic characteristics strongly influence disease presentation and recurrence risk, which may occur more than 5years after initial treatment. Routine genetic testing of PPGL patients is warranted given the high prevalence of mutations, allowing for prognostication and tailored follow-up. In the presence of germline mutations, follow-up should be life-long.

Development and validation of a novel nomogram predicting pseudohypoxia type pheochromocytomas and paragangliomas.

Pseudohypoxia type (PHT) pheochromocytomas and paragangliomas (PPGLs) are more likely to metastasize and have a poor prognosis. However, application of genetic tests has many restrictions. The study aims to establish a novel nomogram for predicting the risk of PHT PPGLs. This retrospective cross-sectional study included 242 patients with pathology confirmed PPGLs in one tertiary care center in China in 2010-2021. Clinical and biochemical characteristics were collected. Next-generation sequencing was performed in all PPGLs patients for detection of mutation. Univariate and multivariable logistic regression analyses were used to select risk factors for constructing the nomogram. The area under the receiver operating characteristic (ROC) curve (AUC) was used to evaluate the discrimination of the nomogram and the calibration curve was performed. Four variables including age ≤ 35years, hypertension, 24h urinary output of urinary vanillylmandelic acid (VMA) ≥ 100 umol/24h and urinary 17-ketosteroide (17KS) ≤ 50 umol/24h levels were independently associated with PHT PPGLs in the logistic regression analysis and were included in the nomogram. The nomogram showed a good discrimination performance with AUC of 0.829 [95% confidence interval (CI), 0.767-0.891] in the training set and 0.797 (95%CI, 0.659-0.935) in the validation set, respectively. The calibration curve showed a bias-corrected AUC of 0.809 vs. 0.795, and a Hosmer-Lemeshow (H-L) test yielded a p value of 0.801 vs. 0.885, indicating the nomogram's good ability to distinguish PHT PPGLs from non-PHT PPGLs. Our study has proposed a novel nomogram for individualized prediction of the PHT PPGLs, which may make contributions to guide the patients' personalized management, follow-up, and treatment.

Initial characterization of immune microenvironment in pheochromocytoma and paraganglioma.

Due to fewer adverse events, faster onset of action, and longer durable responses compared to chemotherapy, immunotherapy has been widely used to treat advanced solid tumors. Moreover, immunotherapy can improve the autoimmune status, thus allowing patients to benefit from the treatment in the long term. The immune microenvironment status is closely associated with the response to chemotherapies. Here, we analyzed the characteristics of the immune microenvironment in pheochromocytoma and paraganglioma (PPGL). Immunohistochemistry showed that PD-L1 is sparely expressed in PPGL with low positive rates and low expression levels, an expression pattern, that is, not correlated with tumor malignancy. Moreover, the level of intratumoral CD4+ and CD8+ lymphocyte infiltration in PPGL is low, suggesting that the immune microenvironment in PPGL may be in "immune desertification" or "immune rejection" states in which CD4+ and CD8+ lymphocyte infiltration is prevented, rendering immunotherapy less effective. In sum, our results indicate that PPGL is a microsatellite-stable tumor with low tumor mutational burden (TMB) levels, weak neoantigen production, and poor tumor antigenicity, hinting at a poor response of PPGL to chemotherapies.

Rates of Pheochromocytoma/Paraganglioma Screening in At-Risk Populations.

Pheochromocytomas and paragangliomas (PPGL) are rare causes of secondary hypertension, but when unrecognized, they can lead to serious complications. Data regarding PPGL screening are lacking. This study aimed to assess the rates and patterns of PPGL screening among eligible patients. We conducted a retrospective review of adults with hypertension seen in outpatient clinics of a large academic center between January 1, 2017, and June 30, 2020. We included patients with treatment-resistant hypertension, hypertension at age < 35 years, and/or adrenal mass(es). Of 203 535 patients with hypertension identified, 71 088 (35%) met ≥ 1 inclusion criteria, and 2013 (2.83%) were screened for PPGL. Patients screened were younger (56.2 ± 17.4 vs 64.0 ± 17.1 years), more often women (54.1% vs 44.2%), and never-smokers (54.6% vs 47.5%, P < 0.001 for all). The rate of screening was highest in patients with hypertension and adrenal mass(es) (51.7%, vs 3.9% in patients with early-onset hypertension, and 2.4% in those with treatment-resistant hypertension). Multivariable logistic regression showed higher odds ratio (OR) of PPGL screening in women (OR [95% CI]: 1.48 [1.34-1.63]); Black vs White patients (1.35 [1.19-1.53]); patients with adrenal mass(es) (55.1 [44.53-68.15]), stroke (1.34 [1.16-1.54]), dyslipidemia (1.41 [1.26-1.58]), chronic kidney disease (1.40 [1.26-1.56]), and obstructive sleep apnea (1.96 [1.76-2.19]). PPGL screening is pursued in roughly half of patients with adrenal nodules and hypertension, but rarely in patients with treatment-resistant or early-onset hypertension. Similar to screening for other forms of secondary hypertension, PPGL screening occurs more often after serious complications develop.

Pseudohypoxia in paraganglioma and pheochromocytoma is associated with an immunosuppressive phenotype.

Metastatic pheochromocytoma and paraganglioma (PPGL) have poor prognosis and limited therapeutic options. The recent advent of immunotherapies showing remarkable clinical efficacies against various cancer types offers the possibility of novel opportunities also for metastatic PPGL. Most PPGLs are pathogenically linked to inactivating mutations in genes encoding different succinate dehydrogenase (SDH) subunits. This causes activation of the hypoxia-inducible factor 2 (HIF2)-mediated transcriptional program in the absence of decreased intratumoral oxygen levels, a phenomenon known as pseudohypoxia. Genuine hypoxia in a tumor creates an immunosuppressive tumor microenvironment. However, the impact of pseudohypoxia in the immune landscape of tumors remains largely unexplored. In this study, tumoral expression of programmed death-ligand 1 (PD-L1) and HIF2α and tumor infiltration of CD8 T lymphocytes (CTLs) were examined in PPGL specimens from 102 patients. We assessed associations between PD-L1, CTL infiltration, HIF2α expression, and the mutational status of SDH genes. Our results show that high PD-L1 expression levels in tumor cells and CTL tumor infiltration were more frequent in metastatic than nonmetastatic PPGL. However, this phenotype was negatively associated with SDH mutations and high HIF2α protein expression. These data were validated by analysis of mRNA levels of genes expressing PD-L1, CD8, and HIF2α in PPGL included in The Cancer Genome Atlas database. Further, PD-L1 and CD8 expression was lower in norepinephrine than epinephrine-secreting PPGL. This in silico analysis also revealed the low PD-L1 or CD8 expression levels in tumors with inactivating mutations in VHL or activating mutations in the HIF2α-coding gene, EPAS1, which, together with SDH-mutated tumors, comprise the pseudohypoxic molecular subtype of PPGL. These findings suggest that pseudohypoxic tumor cells induce extrinsic signaling toward the immune cells promoting the development of an immunosuppressive environment. It also provides compelling support to explore the differential response of metastatic PPGL to immune checkpoint inhibitors. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Low number of neurosecretory vesicles in neuroblastoma impairs massive catecholamine release and prevents hypertension.

Neuroblastoma (NB) is a pediatric cancer of the developing sympathetic nervous system. It produces and releases metanephrines, which are used as biomarkers for diagnosis in plasma and urine. However, plasma catecholamine concentrations remain generally normal in children with NB. Thus, unlike pheochromocytoma and paraganglioma (PHEO/PGL), two other non-epithelial neuroendocrine tumors, hypertension is not part of the usual clinical picture of patients with NB. This suggests that the mode of production and secretion of catecholamines and metanephrines in NB is different from that in PHEO/PGL, but little is known about these discrepancies. Here we aim to provide a detailed comparison of the biosynthesis, metabolism and storage of catecholamines and metanephrines between patients with NB and PHEO. Catecholamines and metanephrines were quantified in NB and PHEO/PGL patients from plasma and tumor tissues by ultra-high pressure liquid chromatography tandem mass spectrometry. Electron microscopy was used to quantify neurosecretory vesicles within cells derived from PHEO tumor biopsies, NB-PDX and NB cell lines. Chromaffin markers were detected by qPCR, IHC and/or immunoblotting. Plasma levels of metanephrines were comparable between NB and PHEO patients, while catecholamines were 3.5-fold lower in NB vs PHEO affected individuals. However, we observed that intratumoral concentrations of metanephrines and catecholamines measured in NB were several orders of magnitude lower than in PHEO. Cellular and molecular analyses revealed that NB cell lines, primary cells dissociated from human tumor biopsies as well as cells from patient-derived xenograft tumors (NB-PDX) stored a very low amount of intracellular catecholamines, and contained only rare neurosecretory vesicles relative to PHEO cells. In addition, primary NB expressed reduced levels of numerous chromaffin markers, as compared to PHEO/PGL, except catechol O-methyltransferase and monoamine oxidase A. Furthermore, functional assays through induction of chromaffin differentiation of the IMR32 NB cell line with Bt2cAMP led to an increase of neurosecretory vesicles able to secrete catecholamines after KCl or nicotine stimulation. The low amount of neurosecretory vesicles in NB cytoplasm prevents catecholamine storage and lead to their rapid transformation by catechol O-methyltransferase into metanephrines that diffuse in blood. Hence, in contrast to PHEO/PGL, catecholamines are not secreted massively in the blood, which explains why systemic hypertension is not observed in most patients with NB.

PD-L1 expression and association with genetic background in pheochromocytoma and paraganglioma.

Metastatic pheochromocytomas and paragangliomas (PPGLs) are rare neuroendocrine tumors associated with poor prognosis and limited therapeutic options. Recent advances in oncology-related immunotherapy, specifically in targeting of programmed cell death-1 (PD-1)/programmed death-ligand 1 (PD-L1) pathways, have identified a new treatment potential in a variety of tumors, including advanced and rare tumors. Only a fraction of patients being treated by immune checkpoint inhibitors have shown to benefit from it, displaying a need for strategies which identify patients who may most likely show a favorable response. Building on recent, promising outcomes in a clinical study of metastatic PPGL using pembrolizumab, a humanized IgG4κ monoclonal antibody targeting the PD-1/PD-L1 pathway, we examined PD-L1 and PD-L2 expression in relation to oncogenic drivers in our PPGL patient cohort to explore whether expression can predict metastatic potential and/or be considered a predictive marker for targeted therapy. We evaluated RNA expression in the NIH cohort of 48 patients with known genetic predisposition (sporadic; pseudohypoxia: SDHB, VHL, EPAS1, EGLN1; kinase signaling: RET, NF1) and 6 normal medulla samples (NAM). For comparison, 72 PPGL samples from The Cancer Genome Atlas (TCGA) were used for analysis of gene expression based on the variant status (pseudohypoxia: SDHB, VHL, EPAS1, EGLN1; kinase signaling: NF1, RET). Expression of PD-L1 was elevated in the PPGL cohort compared to normal adrenal medulla, aligning with the TCGA analysis, whereas PD-L2 was not elevated. However, expression of PD-L1 was lower in the pseudohypoxia cluster compared to the sporadic and the kinase signaling subtype cluster, suggesting that sporadic and kinase signaling cluster PPGLs could benefit from PD-1/PD-L1 therapy more than the pseudohypoxia cluster. Within the pseudohypoxia cluster, expression of PD-L1 was significantly lower in both SDHB- and non-SDHB-mutated tumors compared to sporadic tumors. PD-L1 and PD-L2 expression was not affected by the metastatic status. We conclude that PD-L1 and PD-L2 expression in our cohort of PPGL tumors was not linked to metastatic behavior, however, the presence of PPGL driver mutation could be a predictive marker for PD-L1-targeted therapy and an important feature for further clinical studies in patients with PPGL.

RF33 | PSUN03 Rates of Pheochromocytoma/Paraganglioma Screening in At-Risk Populations

Abstract Background Hypertension is estimated to affect 1: 2 adults in the USA, and secondary hypertension accounts for up to 40% cases. Pheochromocytomas and paragangliomas (PPGL) are thought to be rare causes of hypertension, although their true prevalence might be underestimated. Less than half of patients with PPGL have prototypical symptoms. PPGL can lead to serious complications, including death, particularly if unrecognized. Expert guidelines recommend screening for secondary causes of hypertension in patients with resistant hypertension, patients with early-onset hypertension, and in those with hypertension and an adrenal mass. The rates of PPGL screening are unknown. Objective To evaluate the rates and patterns of PPGL screening among candidate patients. Methods We conducted a retrospective review of adult patients (age ≥ 18 years) with hypertension seen in a university-based outpatient setting between 01/01/2017 - 06/30/2020, and we included patients with: 1) resistant hypertension (uncontrolled hypertension while taking at least 3 antihypertensive agents OR taking ≥4 antihypertensive agents); 2) hypertension at age &amp;lt;35 years; 3) adrenal nodule(s). We excluded patients with renovascular hypertension, advanced chronic kidney disease (CKD stage ≥4), stage III and IV heart failure, adrenal insufficiency, and congenital adrenal hyperplasia. Results Of 203,535 patients with hypertension, 71,088 (35%) met at least one of the above criteria, and only 2013 (2.83%) were screened for PPGL. Overall, patients screened were younger (56.2 ± 17.4 vs. 63.9±17.1 years, p &amp;lt;0.001), more often women (54.1% vs. 44.2%, p=0.001), and non-smokers (54.6% vs. 47.5%, p&amp;lt;0.001) than those not screened. While most patients included in the study were white (80%), the proportion of black patients was larger among those screened (19.9% vs.13.3% of those not screened, p&amp;lt;0.001). Of the three indications for PPGL screening, the rates were highest in patients with hypertension and adrenal nodule(s) (51.7%), while patients with early onset hypertension and those with resistant hypertension were rarely screened (3.9% and 2.4%, respectively). Multivariable logistic regression with LASSO selection showed that the odds of PPGL screening were higher in black vs. white patients (1.35 [1.19-1.53]); those who never smoked (1.68 [1.41-2.00]); patients with stroke (1.34 [1.16-1.54]); dyslipidemia (1.41 [1.26-1.57]), CKD (1.40 [1.26-1.56); obstructive sleep apnea (1.96 [1.76-2.19]); and adrenal nodules (55.1 [44.53-68.17]). Conclusions Screening for PPGL is conducted in roughly half of patients with adrenal nodules and hypertension, but rarely in patients with resistant or early onset hypertension. Screening occurs more often in patients with complications known to be associated with PPGL, including cardiovascular accidents. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m., Monday, June 13, 2022 1:12 p.m. - 1:17 p.m.

ODP583 Screening for Pheochromocytoma in a Cohort of Patients with Takotsubo Cardiomyopathy: New insights on Prevalence and Screening Tests Reliability Surrounding the Acute Cardiac Event

Abstract Background According to Takotsubo cardiomyopathy (TCM) diagnostic criteria, pheochromocytoma and paraganglioma (PPGL) should be excluded as secondary causes. However, it is unclear whether PPGL screening in the setting of acute TCM is reliable. We aimed to assess the prevalence of PPGL and the reliability of PPGL screening in a cohort of patients with TCM. Method: We retrospectively reviewed data from patients admitted in a tertiary hospital between August 2012 and January 2021 with a diagnosis of TCM proven by typical echocardiography findings and no acute occlusion on coronarography, who were screened for PPGL by plasma metanephrines/normetanephrines (M/NM). If the first screening was positive, a second plasma M/NM sample was used for confirmation. Time between TCM diagnosis and PPGL screening was collected. Results Among 64 patients identified with TCM, 42 underwent plasma M/NM screening. 81. 0% were female, and the mean age was 67.4 ± 9.9 years old. Ten patients (23.8%) had a positive result. Of those, 8 patients had a weakly positive result (1-2×upper limit of normal [ULN]) and 2 had a strongly positive result (&amp;gt;2×ULN). Of those 10 patients, 6 underwent a second screening: 5 had a normal result and 1 had a weakly positive result (plasma NM 1. 06×ULN). This patient underwent a third screening that was negative. In addition, an abdominal CT showed normal adrenal glands, and their chromogranin A levels were normal. Four patients had a positive initial PPGL screening, but they did not undergo a second screening: 3 died of causes unrelated to TCM before a second plasma M/NM sample was taken and one patient was lost to follow-up (his plasma NM was weakly positive at 1.29×ULN). They all had an abdominal CT that showed normal adrenal glands. Average time between TCM diagnosis and PPGL screening in all patients and in patients with a positive initial screening was 4.57 ± 3.91 and 3.38 ± 2.12 days, respectively. A linear regression model suggested an inverse relationship between plasma M/NM and time between TCM diagnosis and screening, with R2 = 0.2275. Conclusion TCM occurring as the initial presentation of PPGL is rare. All patients with a positive screening ended up being false positives in our study. The ratio of false positive results when screening for PPGL in the setting of acute TCM seems to be higher than in the general population, which could be explained by a hyperadrenergic state. It is unclear whether a shorter delay between TCM diagnosis and PPGL screening may be associated with more false positives. More research is needed to determine what is the optimal timing for PPGL screening in acute TCM and if higher cut-offs should be used to minimize false positive results. Presentation: No date and time listed

Sex-related Differences in a Canadian Cohort of Patients With Pheochromocytomas and Paragangliomas

The distinctions between biological males and females have long been ignored in the field of research. Our objective was to evaluate sex-related differences in signs and symptoms in a cohort of patients with pheochromocytomas and paragangliomas (PPGLs).

PSUN28 Factors Associated with False-positive Fractionated Metanephrines in Plasma and Urine

Abstract Context Plasma and 24-hr urine metanephrine (M) and normetanephrine (NM) are the standard of care tests used in the biochemical diagnosis of pheochromocytoma and paraganglioma (PPGL). Considering the rarity of PPGL, false positive (FP) results represent a challenge because they lead to additional investigations, healthcare burden, and uncertainty for the patient. The impact of medications on the rate of FP results is not fully established. Objective We aimed to identify the medications associated with the FP rate of 24-hr urine and plasma M and NM measured by the HPLC-MS/MS method. Methods We conducted a single-center study of patients who had 24-hour urine or plasma M and NM testing between 09/27/2015 and 02/15/2021, and who had a follow-up of at least 6 months. Results were considered FP if M/NM were &amp;gt; upper limit of the normal ranges (ULN) and there was absence of PPGL. Results were considered true negative (TN) when M/NM were within the reference ranges in patients without PPGL. Age- and sex-adjusted odds ratios (OR) and 95% confidence intervals (CI) were calculated using logistic regression models. Results Plasma M/NM testing was performed in 3152 patients and 24-hr urine M/NM was performed in 2008 patients. The FP rate for the M fraction (plasma: 0.8%, urine: 1.3%) was much lower than the FP rate for NM (plasma: 16%, urine: 4.4%); thus, the impact of medications on FP rate was examined only for NM. In those with FP NM, the median degrees of elevation were 24% (IQR 10-46) &amp;gt;ULN in plasma and 26% (IQR 11-45) &amp;gt;ULN in urine. When compared to patients with TN results, patients with FP plasma NM were more likely to be treated with opioids (OR=1.29, 95%CI, 1.04-1.60), tricyclic antidepressants (OR=1.61, 95%CI,1.14-2.27), serotonin–norepinephrine reuptake inhibitors (OR=1.85, 95%CI, 1.35-2.53), second generation antipsychotics (OR=2.32, 95%CI, 1.28-4.20), but not first generation antipsychotics (OR=1.23, 95% CI, 0.86-1.75) when compared to the TN group. When compared to patients with TN results, patients with FP urine NM were more likely to be treated with opioids (OR=1.96 95%CI, 1.26-3.06), tricyclic antidepressants (OR=2.61, 95%CI, 1.47-4.65), serotonin–norepinephrine reuptake inhibitors (OR=2.20, 95%CI, 1.20-4.02), and both first (OR=3.06, 95%CI, 1.74-5.38) and second generation antipsychotics (OR=2.51, 95%CI, 1.03-6.13). Conclusion The plasma NM FP rate was 16% and 3-fold higher than the same measurement in urine (4.4%). Several classes of medications had a significant impact on the rate of FP NM. Clinicians should consider use of 24-hr urine M and NM in low suspicion cases of PPGL where the diagnosis simply needs to be excluded. Presentation: Sunday, June 12, 2022 12:30 p.m. - 2:30 p.m.