A single fasting plasma 5-HIAA value correlates with 24-hour urinary 5-HIAA values and other biomarkers in midgut neuroendocrine tumors (NETs)

Smart dual imprinted Origami 3D-ePAD for selective and simultaneous analysis of vanillylmandelic acid and 5-hydroxyindole-3-acetic acid carcinoid cancer biomarkers using graphene quantum dots coated with dual molecularly imprinted polymers

Measuring the levels of the biomarkers vanillylmandelic acid (VMA) and 5-Hydroxyindole-3-acetic acid (5-HIAA) is a valuable tool for clinical diagnosis not only of neuroblastoma or carcinoid syndrome, but also of essential hypertension, depression, migraine, and Tourette's syndrome. Herein, we explore using graphene quantum dots (GQDs) coated with molecularly imprinted polymer (MIP) as novel dual-imprinted sensors for selective and simultaneous determination of VMA and 5-HIAA in urine and plasma samples. The dual-MIP was successfully coated on the GQDs core via co-polymerization of (3-aminopropyl) triethoxysilane (APTES) and tetraethyl orthosilicate (TEOS), acting as functional and cross-linking monomers, respectively. In addition, we successfully created the dual imprinted VMA and 5-HIAA shell on the GQDs' core via a one-pot synthesis. We fabricated a facile and ready-to-use Origami three-dimensional electrochemical paper-based analytical device (Origami 3D-ePAD) for simultaneous determination of VMA and 5-HIAA using a GQDs@dual-MIP modified graphene electrode (GQDs@dual-MIP/SPGE). The Origami 3D-ePAD was designed to form a voltammetric cell on a three-layer foldable sheet with several advantages. For example, they were quickly assembled and enhanced the device's physical durability with the hydrophobic backup sheet. The developed dual imprinted Origami 3D-ePAD leads to substantially enhanced sensitivity and selectivity to electrochemical signal amplification generated from increasing the electrode-specific surface area, electrocatalytic activity, and the large numbers of dual imprinted sites for VMA and 5-HIAA detection. The synthetic recognition sites are highly selective for 5-HIAA and VMA molecules with an imprinting factor of 8.46 and 7.10, respectively. Quantitative analysis relying on square wave voltammetry reveals excellent linear dynamic ranges of around 0.001-25 μM, with detection limits of 0.023 nM for 5-HIAA and 0.047 nM for VMA (3Sb, n = 3). The Origami 3D-ePAD provides high accuracy and precision (i.e., recovery values of 5-HIAA ranged from 82.98 to 98.40 %, and VMA ranged from 83.28 to 104.39 %), and RSD less than 4.37 %) in urine and plasma samples without any evidence of interference. Hence, it is well suited as a facile and ready-to-use disposable device for point-of-care testing. It is straightforward, cost-effective, reproducible, and stable. Furthermore, it allows for rapid analysis (analysis time ∼20s) useful in medical diagnosis and other relevant fields.

Plasma tryptophan pathway metabolites quantified by liquid chromatography-tandem mass spectrometry as biomarkers in neuroendocrine tumor patients

A good and accessible biomarker is of great clinical value in neuroendocrine tumor (NET) patients, especially considering its frequently indolent nature and long-term follow-up. Plasma chromogranin A (CgA) and 5-hydroxyindoleacetic acid (5-HIAA) are currently used as biomarkers in NET, but their sensitivity and specificity are restricted. 5-HIAA is the main metabolite of serotonin, an important neurotransmitter of the tryptophan pathway. The aim of this study is to estabish a sensitive and accurate method for the quantification of tryptophan pathway metabolites in plasma. We further aimed to evaluate its utility as a clinical tool in NET disease. We obtained plasma samples from NET patients and healthy controls recruited from the University Hospital of North Norway, Tromsø. Samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), and eight metabolites of the tryptophan pathway were quantified. We included 130 NET patients (72/130 small intestinal [SI] NET, 35/130 pancreatic NET, 23/130 other origin) and 20 healthy controls. In the SI-NET group, 26/72 patients presented with symptoms of carcinoid syndrome (CS). We found that combining tryptophan metabolites into a serotonin/kynurenine pathway ratio improved diagnostic sensitivity (92.3%) and specificity (100%) in detecting CS patients from healthy controls compared with plasma 5-HIAA alone (sensitivity 84.6%/specificity 100%). Further, a clinical marker based on the combination of plasma serotonin, 5-HIAA, and 5OH-tryptophan, increased diagnostic capacity identifying NET patients with metastasized disease from healthy controls compared with singular plasma 5-HIAA, serotonin, or CgA. In addition, this marker was positive in 61% of curatively operated SI-NET patients compared with only 10% of healthy controls (p < .001). Our results indicate that simultaneous quantification of several tryptophan metabolites in plasma, using LC-MS/MS, may represent a clinically useful diagnostic tool in NET disease.

Heteroatoms chemical tailoring of aluminum nitrite nanotubes as biosensors for 5-hydroxyindole acetic acid (a biomarker for carcinoid tumors): insights from a computational study

This study aims to elucidate the properties of aluminum nitrite nanotubes (AlNNT) encapsulated with phosphorus (P@AlNNT), sulphur (S@AlNNT), and silicon (Si@AlNNT) heteroatoms for use as biosensors for 5-hydroxyindoleacetic acid (5HIAA).

The Quest for Circulating Biomarkers in Neuroendocrine Neoplasms: a Clinical Perspective

OPINION STATEMENT

Given the considerable heterogeneity in neuroendocrine neoplasms (NENs), it appears unlikely that a sole biomarker exists capable of fully capturing all useful clinical aspects of these tumors. This is reflected in the abundant number of biomarkers presently available for the diagnosis, prognosis, and monitoring of NEN patients. Although assessment of immunohistochemical and radiological markers remains paramount and often obligatory, there has been a notable surge of interest in circulating biomarkers over the years given the numerous benefits associated with liquid biopsies. Currently, the clinic primarily relies on single-analyte assays such as the chromogranin A assay, but these are far from ideal because of limitations such as compromised sensitivity and specificity as well as a lack of standardization. Consequently, the quest for NEN biomarkers continued with the exploration of multianalyte markers, exemplified by the development of the NETest and ctDNA-based analysis. Here, an extensive panel of markers is simultaneously evaluated to identify distinct signatures that could enhance the accuracy of patient diagnosis, prognosis determination, and response to therapy prediction and monitoring. Given the promising results, the development and implementation of these multianalyte markers are expected to usher in a new era of NEN biomarkers in the clinic. In this review, we will outline both clinically implemented and more experimental circulating markers to provide an update on developments in this rapidly evolving field.

Plasma or serum 5-hydroxyindoleacetic acid can be used interchangeably in patients with neuroendocrine tumours

5-hydroxyindole acetic acid, a metabolite of serotonin, is used in the diagnosis and monitoring of patients with neuroendocrine tumours, in particular patients with small intestinal neuroendocrine tumours associated with the carcinoid syndrome. Analysis of 5-hydroxyindole acetic acid was commonly performed in urine, but blood-based assays are now becoming available. The objective of this study was to assess how 5-hydroxyindole acetic acid compares in plasma and serum as a biochemical marker of neuroendocrine tumours. Twenty-four-hour urine, plasma and serum samples were obtained from 80 patients with neuroendocrine tumours and 30 healthy volunteers. We developed a liquid chromatography tandem mass spectrometry assay for plasma and serum 5-hydroxyindole acetic acid. Comparison was made between them, and their cut-off was determined using a receiver-operating characteristic curve. A close correlation was shown between plasma and serum 5-hydroxyindole acetic acid. At a cut-off of 135 nmol/l, a sensitivity of 91.2% with a specificity of 61.9% was obtained for both compared to the urinary assay. A statistically significant agreement was shown when plasma and serum 5-hydroxyindole acetic acid were compared with the currently used urine assay in patients with neuroendocrine tumours; κ = 0.675 (95% CI 0.49 to 0.86), p < 0.001 and healthy volunteers; 0.967 (95% CI 0.828 to 0.999), p = <0.001. In conclusion, 5-hydroxyindole acetic acid in plasma and serum were comparable, hence either sample type can be used interchangeably.

Circulating tumour cells and tumour biomarkers in functional midgut neuroendocrine tumours

CALM-NET was a phase IV exploratory study in the UK that aimed to evaluate if the presence of circulating tumour cells (CTCs) at baseline predicted symptomatic response in patients with midgut neuroendocrine tumours (NETs) treated with lanreotide autogel (LAN). Adults with functional, well/moderately differentiated (Ki-67 <20%) midgut NETs received LAN 120 mg/28 days for 1 year. CTCs were present in blood if enumeration was >0. Primary endpoint was the clinical value of baseline CTCs to predict symptomatic response (decrease in diarrhoea or flushing of ≥50% frequency, or ≥1 severity level). Other endpoints included progression-free survival (PFS) and correlations between plasma and urinary biomarkers (including 5-hydroxyindoleacetic acid [5-HIAA]). Fifty patients were enrolled; 40 completed the study. Baseline CTCs were present in 22 (45.8%) patients (missing baseline CTC status n = 2). Overall, 87.5% (95% confidence interval [CI]: 73.9; 94.5) of patients had a symptomatic response; a 5.9-fold higher odds of symptomatic response in patients without CTC versus patients with CTC at baseline was observed, although this was not statistically significant (odds ratio: 0.17 [95% CI: 0.02; 1.65], p = .126). One-year PFS rate was 66.4% (95% CI: 48.8; 79.2). Biomarker concentrations did not correlate to baseline CTC status. However, there was a strong correlation between plasma and urinary 5-HIAA (Spearman correlation coefficients ≥0.87 [p < .001], all time points). In conclusion, patients without CTC at baseline may be more likely to achieve a symptomatic response following LAN treatment than patients with CTC. Plasma 5-HIAA correlated with urinary 5-HIAA during LAN treatment. ClinicalTrials.gov identifier: NCT02075606.

Role of Somatostatin Signalling in Neuroendocrine Tumours

Somatostatin (SST) is a small peptide that exerts inhibitory effects on a wide range of neuroendocrine cells. Due to the fact that somatostatin regulates cell growth and hormone secretion, somatostatin receptors (SSTRs) have become valuable targets for the treatment of different types of neuroendocrine tumours (NETs). NETs are a heterogeneous group of tumours that can develop in various parts of the body, including the digestive system, lungs, and pituitary. NETs are usually slow growing, but they are often diagnosed in advanced stages and can display aggressive behaviour. The mortality rate of NETs is not outstandingly increased compared to other malignant tumours, even in the metastatic setting. One of the intrinsic properties of NETs is the expression of SSTRs that serve as drug targets for SST analogues (SSAs), which can delay tumour progression and downregulate hormone overproduction. Additionally, in many NETs, it has been demonstrated that the SSTR expression level provides a prognostic value in predicting a therapeutic response. Furthermore, higher a SSTR expression correlates with a better survival rate in NET patients. In recent studies, other epigenetic regulators affecting SST signalling or SSA–mTOR inhibitor combination therapy in NETs have been considered as novel strategies for tumour control. In conclusion, SST signalling is a relevant regulator of NET functionality. Alongside classical SSA treatment regimens, future advanced therapies and treatment modalities are expected to improve the disease outcomes and overall health of NET patients.

Recent Advances in the Diagnosis and Management of Carcinoid Syndrome

Carcinoid syndrome, a paraneoplastic condition linked with the release of multiple humoral factors, affects around 30-40% of patients with well-differentiated neuroendocrine tumours. Carcinoid syndrome has a major and unfavourable impact on patients' quality of life; it raises costs when compared to non-functioning neuroendocrine tumours; and it causes patients' lifestyles to alter, such as food, job, physical activity, and social life. Somatostatin analogues have been the first-line therapy for individuals with neuroendocrine tumours and carcinoid disease for decades. While these drugs give considerable relief from carcinoid syndrome symptoms, clinical progression is unavoidable, necessitating further research into newer treatment measures. Carcinoid tumours are sometimes difficult to diagnose because of their vague or nonspecific symptoms. There have been several advancements in all aspects of carcinoid syndrome, as well as novel therapeutics, in the previous few years. New epidemiological studies show that it is becoming more common; increasing insights into the pathogenesis of its various clinical manifestations and its natural history: definition of prognostic factors; new methods to verify its presence; the development of new drugs to treat its various manifestations, both initially and in somatostatin-refractory cases; and an increased understanding of the pathogenesis, natural history, and management of the disease. An all language literature search was conducted on MEDLINE, COCHRANE, EMBASE, and Google Scholar till November 2021. The following search strings and Medical Subject Headings (MeSH) terms were used: "Recent advances", "Carcinoid syndrome", "Neuroendocrine Neoplasms" and "Carcinoid heart disease". We comprehensively reviewed the literature on the pathogenesis, clinical features, and newer treatment modalities for Carcinoid Syndrome. Recent advancements in research and management have resulted from advances in our understanding of the aetiology of carcinoid syndrome. The development of molecular indicators of aggressiveness improved serum tumour markers, and the molecular aetiology of carcinoid heart disease are all possible because of advances in molecular biology. We conducted a comprehensive review to update knowledge regarding the pathophysiology, diagnostic protocols, and current and newer treatments for carcinoid syndrome, which presently requires a multidisciplinary approach, due to the complexity of the illness's aetiology, diagnosis, and therapy.

Biomarkers in Small Intestine NETs and Carcinoid Heart Disease: A Comprehensive Review

Simple Summary

Neuroendocrine tumors (NET), a heterogeneous group of tumors arising from neuroendocrine cells, often pose a diagnostic and therapeutic challenge for the clinician. Biomarkers can serve as a useful diagnostic, prognostic, and predictive tool in the management of these rare tumors. For years the field of NET biomarkers was mainly based on products se-creted by neuroendocrine tumor cells, however, during the last decade the development of nov-el multianalyte biomarkers has rapidly evolved the field. The aim of this review is to summa-rize the literature on the use and limitations of available NET biomarkers for the diagnosis and management of small intestine neuroendocrine tumors (SI-NETs) and carcinoid heart disease.

Abstract

Biomarkers remain a valuable tool for the diagnosis and management of Neuroendocrine tumors (NETs). Traditional monoanalyte biomarkers such as Chromogranin A (CgA) and 5-Hydrocyondoleacetic acid (5-HIAA) have been widely used for many years as diagnostic, predictive and prognostic biomarkers in the field of NETs. However, the clinical utility of these molecules often has limitations, mainly inherent to the heterogeneity of NETs and the fact that these tumors can often be non-secretory. The development of new molecular multianalyte biomarkers, especially the mRNA transcript based “NETest”, has rapidly evolve the field and gives the ability for a “liquid biopsy” which can reliably assess disease status in real time. In this review we discuss the use of established and novel biomarkers in the diagnosis and management of small intestine NETs and carcinoid heart disease.

Comparison of Serum and Urinary 5-Hydroxyindoleacetic Acid as Biomarker for Neuroendocrine Neoplasms

CONTEXT

Patients with serotonin-secreting neuroendocrine neoplasms (NENs) have increased serum 5-hydroxyindoleacetic acid (5HIAA) concentrations. Serum 5HIAA thus serves as a biomarker in NEN.

OBJECTIVE

To evaluate an improved tandem mass spectrometric serum 5HIAA assay for diagnosis and follow-up of NEN in a clinical cohort.

DESIGN

A retrospective study during 2016-2018 at the Diagnostic Center and Department of Endocrinology at Helsinki University Hospital, Finland.

METHODS

Detailed patient data was obtained from 116 patients. Serum 5HIAA was analyzed by 2 different liquid chromatography with tandem mass spectrometry (LC-MS/MS) assays with samples prepared either by protein precipitation or solid phase extraction. Twenty-four-hour urine 5HIAA samples (n = 33) were analyzed by amperometric LC, and the results were compared. Specificity and sensitivity were calculated by receiver operating characteristic (ROC) analysis.

RESULTS

We achieved 5 to10 000 nmol/L linearity and ≤2.5% variation with our new serum 5HIAA assay. In ROC analysis, the area under curve was 85% by serum assays [upper reference limit (URL) value 123 nmol/L] and 88% by the 24-h urine 5HIAA assay (URL value of 47.1 µmol), respectively. A difference (P < 0.001) between patients with active NEN and patients in remission was found by all 5HIAA assays.

CONCLUSION

Serum 5HIAA by LC-MS/MS after protein precipitation performs equally well for the diagnosis of NEN as urinary 5HIAA LC assay. The outcome and sensitivity for serum and 24-h urine assays are convergent. Due to much more reliable and convenient sampling, we recommend serum instead of 24-h urine 5HIAA for diagnosis and follow-up of NEN patients.

Ultrafast LC-MS/MS analysis of 5-hydroxyindoleacetic acid (5-HIAA) in serum

A very quick and easy LC-MS/MS analysis method for 5-HIAA (5-hydoxyindoleacetic acid) has been developed. The method was fully validated and proved to work well in a clinical setting. Precision at the upper reference limit 123 nmol/L was 3,3% CV. Accuracy ranged from 96% at low levels (50-100 nmol/L) to 99.7% at high levels (500 nmol/L). A previously reported reference interval of 35-123 nmol/L was confirmed as valid based on analysis of 40 samples from voluntary blood donors.

Plasmatic and Urinary 5-Hydroxyindolacetic Acid Measurements in Patients With Midgut Neuroendocrine Tumors: A GTE Study

CONTEXT

Although 24-hour urinary 5-hydroxyindolacetic acid (24u5HIAA) is a key biomarker in midgut neuroendocrine tumors (NETs), it may be inaccurate and inconvenient.

OBJECTIVE

We compared the diagnostic performances of 24u5HIAA, overnight urinary 5HIAA (Ou5HIAA), and plasmatic 5HIAA (p5HIAA) in midgut NETs.

METHODS

This prospective, multicenter study included 80 patients with metastatic midgut NETs and 17 control patients with irritable bowel syndrome. 24u5HIAA, Ou5HIAA, and p5HIAA were measured in urine and plasma collected on 2 consecutive days following a specific recommended diet. Reproducibility of the biomarkers was evaluated by the Spearman test. Diagnostic performance was assessed by the area under the receiver operating characteristic curve (AUROC). Correlations with the main clinical features and declared observance to the specific diet were assessed using AUROC and logistic regression models.

RESULTS

The reproducibility of 24u5HIAA, Ou5HIAA, and p5HIAA were excellent (ρ = 0.916; 0.897; 0.978, respectively, P < .001) with significant discrimination between patients and controls (AUROC = 0.795, P < .001; 0.757, P = .001; 0.717, P = .005, respectively). All 3 markers were correlated with the presence of carcinoid syndrome (AUROC = 0.702, P = .006; 0.701, P = .006; 0.697, P = .007, respectively), carcinoid heart disease (AUROC = 0.896; 0.887; 0.923, P < .001, respectively, P < .001), and liver metastatic involvement greater than 30% (AUROC = 0.827; 0.807; 0.849, P < .001, respectively, P < .001), independent from other traditional prognostic factors. Biomarker levels were similar between patients with optimal or suboptimal diet observance.

CONCLUSION

Ou5HIAA and p5HIAA could be used as more convenient alternatives to 24u5HIAA in patients with metastatic midgut NETs. Prospective long-term studies with repeated dosages are needed.

Serotonin pathway in carcinoid syndrome: Clinical, diagnostic, prognostic and therapeutic implications

Carcinoid syndrome represents the most common functional syndrome that affects patients with neuroendocrine neoplasms. Its clinical presentation is really heterogeneous, ranging from mild and often misdiagnosed symptoms to severe manifestations, that significantly worsen the patient's quality of life, such as difficult-to-control diarrhoea and fibrotic complications. Serotonin pathway alteration plays a central role in the pathophysiology of carcinoid syndrome, accounting for most clinical manifestations and providing diagnostic tools. Serotonin pathway is complex, resulting in production of biologically active molecules such as serotonin and melatonin, as well as of different intermediate molecules and final metabolites. These activities require site- and tissue-specific catalytic enzymes. Variable expression and activities of these enzymes result in different clinical pictures, according to primary site of origin of the tumour. At the same time, the biochemical diagnosis of carcinoid syndrome could be difficult even in case of typical symptoms. Therefore, the accuracy of the diagnostic methods of assessment should be improved, also attenuating the impact of confounding factors and maybe considering new serotonin precursors or metabolites as diagnostic markers. Finally, the prognostic role of serotonin markers has been only evaluated for its metabolite 5-hydroxyindole acetic acid but, due to heterogeneous and biased study designs, no definitive conclusions have been achieved. The most recent progress is represented by the new therapeutic agent telotristat, an inhibitor of the enzyme tryptophan hydroxylase, which blocks the conversion of tryptophan in 5-hydroxy-tryptophan. The present review investigates the clinical significance of serotonin pathway in carcinoid syndrome, considering its role in the pathogenesis, diagnosis, prognosis and therapy.

Surgery and Perioperative Management in Small Intestinal Neuroendocrine Tumors

Small-intestinal neuroendocrine tumors (SI-NETs) are the most prevalent small bowel neoplasms with an increasing frequency. In the multimodal management of SI-NETs, surgery plays a key role, either in curative intent, even if R0 resection is feasible in only 20% of patients due to advanced stage at diagnosis, or palliative intent. Surgeons must be informed about the specific surgical management of SI-NETs according to their hormonal secretion, their usual dissemination at the time of diagnosis and the need for bowel-preserving surgery to avoid short bowel syndrome. The aim of this paper is to review the surgical indications and techniques, and perioperative and postoperative management of SI-NETs.

Emerging role of clinical mass spectrometry in pathology

Mass spectrometry-based assays have been increasingly implemented in various disciplines in clinical diagnostic laboratories for their combined advantages in multiplexing capacity and high analytical specificity and sensitivity. It is now routinely used in areas including reference methods development, therapeutic drug monitoring, toxicology, endocrinology, paediatrics, immunology and microbiology to identify and quantify biomolecules in a variety of biological specimens. As new ionisation methods, instrumentation and techniques are continuously being improved and developed, novel mass spectrometry-based clinical applications will emerge for areas such as proteomics, metabolomics, haematology and anatomical pathology. This review will summarise the general principles of mass spectrometry and specifically highlight current and future clinical applications in anatomical pathology.

Quantitative Profiling of Platelet-Rich Plasma Indole Markers by Direct-Matrix Derivatization Combined with LC-MS/MS in Patients with Neuroendocrine Tumors

BACKGROUND

Currently, several indole markers are measured separately to support diagnosis and follow-up of patients with neuroendocrine tumors (NETs). We have developed a sensitive mass spectrometry method that simultaneously quantifies all relevant tryptophan-related indoles (tryptophan, 5-hydroxytryptophan, serotonin, 5-hydroxyindoleacetic acid) in platelet-rich plasma. Direct-matrix derivatization was used to make the chemical properties of the indoles uniform and to improve the analytical sensitivity and specificity of the assay.

METHODS

In situ derivatization was performed directly in platelet-rich plasma with propionic anhydride at an ambient temperature. The derivatized indoles were extracted by online solid-phase extraction and eluted to the analytical column for separation followed by mass spectrometric detection. The method was validated according to international guidelines. Platelet-rich plasma samples from 68 healthy individuals and 40 NET patients were analyzed for tryptophan, 5-hydroxytryptophan, serotonin, and 5-hydroxyindoleacetic acid.

RESULTS

The method reproducibly quantified relevant indoles in 8.5 min, including online sample cleanup. Intra- and interassay imprecision, evaluated at 3 different concentrations, ranged from 2.0% to 12% and 1.9% to 13%, respectively. The limit of quantification was sufficient to measure endogenous concentrations of all 4 indoles. Healthy individuals and NET patients had different concentrations of 5-hydroxytryptophan, serotonin, and 5-hydroxyindoleacetic acid, but tryptophan concentrations were the same.

CONCLUSIONS

Direct-matrix derivatization in combination with LC-MS/MS is a powerful tool for the simultaneous quantification of all tryptophan-related indoles in platelet-rich plasma. Simultaneous profiling of relevant indoles improves the biochemical characterization and follow-up of NETs.

The role of 5-hydroxyindoleacetic acid in neuroendocrine tumors: the journey so far

5-Hydroxyindole acetic acid (5-HIAA) is a surrogate marker for serotonin measurement and one of the first biochemical markers used in neuroendocrine tumors. In this review, we give a brief history of 5-HIAA and its precursor serotonin. We discuss its clinical utility and diagnostic performance in small intestinal neuroendocrine tumor and describe the challenges encountered during its analysis, historically performed in urine. The introduction of blood-based assays will help overcome some of the issues associated with its measurement in urine. The diagnostic performance of serum and plasma 5-HIAA has been shown to be comparable to that of urine 5-HIAA. Thus, analysis in either serum or plasma will provide a practical and convenient alternative to urine.

Measurement of urinary 5-HIAA: correlation between spot versus 24-h urine collection

BACKGROUND

The 24-h urinary output of 5-hydroxyindoleacetic acid (5-HIAA) is used to monitor disease progression and treatment responses of neuroendocrine neoplasms (NENs). Several conditions are required for 5-HIAA assay, involving urine collection/preservation and food/drug restrictions.

AIM

To evaluate the correlation between 5-HIAA concentration in a spot urine sample and the output in a 24-h urine collection, and whether spot urine specimens can replace 24-h collection.

METHODS

Patients with NENs or symptoms suggestive of NENs were asked to provide a separate spot urine at the end of the 24-h urine collection for 5-HIAA assessment. The upper reference limit for 24-h urinary 5-HIAA was 40 µmol/24 h. 5-HIAA measurements in spot urine samples were corrected for variation in urine flow rate by expressing results as a ratio to creatinine concentration.

RESULTS

We included 136 paired urinary samples for 5-HIAA assessment from 111 patients (100 NENs). The correlation between 5-HIAA values measured in 24-h and spot urines was r = +0.863 (P < 0.001) and r = +0.840 (P < 0.001) including only NEN patients. Using the 24-h urinary 5-HIAA as reference method, the AUC on ROC analysis for spot urinary 5-HIAA was 0.948 (95% CI, 0.914-0.983; P < 0.001), attaining a sensitivity of 83% and specificity of 95% using 5.3 mol/mmol as cut-off for the spot urine. The AUC among NEN patients alone was 0.945 (95% CI, 0.904-0.987; P < 0.001).

CONCLUSIONS

The ratio of 5-HIAA to creatinine in a spot urine could replace the measurement of 5-HIAA output in a 24-h urine collection, especially for follow-up of patients with known elevated 5-HIAA levels.

Carcinoid Syndrome: Updates and Review of Current Therapy

OPINION STATEMENT

Carcinoid syndrome (CS) is a complex disorder caused by functional neuroendocrine tumors (NETs). This debilitating disease is characterized by hyper-secretion of biologically active substances eliciting major hormonal symptoms burden and fibrotic changes that are often challenging for management. There have been a number of insights that have substantially advanced treatments since the introduction of somatostatin analogs (SSAs). Second-line treatments are needed in a substantial proportion of patients with advanced disease that have uncontrolled hormone secretion on the highest labeled doses of SSAs. International guidelines suggest several available options including dose escalation of SSAs, interferon alpha, everolimus, radionuclide therapy, liver-directed therapies, and the novel tryptophan hydroxylase 1 inhibitor, telotristat ethyl. The clear preference of one second-line therapy over the other is not stated since their relative and long-term efficacy are largely unknown, and standardized approach of hormonal response assessment is lacking in the literature. In the clinical setting, the treatment of CS is guided in conjunction with patients' performance status, tumor origin, grade, stage, and growth rate, with regard to both anti-hormonal, as well as anti-proliferative effect. There is an unmet need for further well-designed randomized placebo-controlled and head-to-head studies that systematically assess CS symptom control and biochemical response following a specific intervention.

Recent Trends in the Quantification of Biogenic Amines in Biofluids as Biomarkers of Various Disorders: A Review

Biogenic amines (BAs) are bioactive endogenous compounds which play a significant physiological role in many cell processes like cell proliferation and differentiation, signal transduction and membrane stability. Likewise, they are important in the regulation of body temperature, the increase/decrease of blood pressure or intake of nutrition, as well as in the synthesis of nucleic acids and proteins, hormones and alkaloids. Additionally, it was confirmed that these compounds can be considered as useful biomarkers for the diagnosis, therapy and prognosis of several neuroendocrine and cardiovascular disorders, including neuroendocrine tumours (NET), schizophrenia and Parkinson's Disease. Due to the fact that BAs are chemically unstable, light-sensitive and possess a high tendency for spontaneous oxidation and decomposition at high pH values, their determination is a real challenge. Moreover, their concentrations in biological matrices are extremely low. These issues make the measurement of BA levels in biological matrices problematic and the application of reliable bioanalytical methods for the extraction and determination of these molecules is needed. This article presents an overview of the most recent trends in the quantification of BAs in human samples with a special focus on liquid chromatography (LC), gas chromatography (GC) and capillary electrophoresis (CE) techniques. Thus, new approaches and technical possibilities applied in these methodologies for the assessment of BA profiles in human samples and the priorities for future research are reported and critically discussed. Moreover, the most important applications of LC, GC and CE in pharmacology, psychology, oncology and clinical endocrinology in the area of the analysis of BAs for the diagnosis, follow-up and monitoring of the therapy of various health disorders are presented and critically evaluated.

Phyto-sesquiterpene lactone deoxyelephantopin and cisplatin synergistically suppress lung metastasis of B16 melanoma in mice with reduced nephrotoxicity

BACKGROUND

Cisplatin (CP) is a chemotherapeutic drug for treating melanoma that also causes adverse side effects in cancer patients.

PURPOSE

This study investigated the bioefficacy of a phytoagent deoxyelephantopin (DET) in inhibiting B16 melanoma cell activity, its synergism with CP against metastatic melanoma, and its capability to attenuate CP side effects in animals.

METHODS

DET and CP bioactivities were assessed by MTT assay, isobologram analysis, time-lapse microscopy, migration and invasion assays, flow cytometry and western blotting. In vivo bioluminescence imaging was used to detect lung metastasis of B16 cells carrying COX-2 reporter gene in syngeneic mice. H&E staining and immunohistochemistry were used to evaluate the compound/drug efficacy and CP side effects. Nephrotoxicity caused by CP treatment in mice was evaluated by UPLC/ESI-QTOF MS - based metabolomics and haematometry.

RESULT

DET, alone or in combination with cisplatin, inhibited B16 cell proliferation, migration, and invasion, and induced cell-cycle arrested at the G₂/M phase and de-regulated cell-cycle mediators in cancer cells. In a murine B16^COX-Luc metastatic allograft model, CP2 (2  mg/kg) treatment inhibited B16 lung metastasis accompanied by severe body weight loss, renal damage and inflammation, and haematological toxicity. DET10 and CP cotreatment (DET10 + CP1) or sequential treatment (CP2→DET10) significantly inhibited formation of pulmonary melanoma foci and reduced renal damage. DET pretreatment (Pre-DET10) or CP2→DET10 treatment had the longest survival (52  vs. 37 days for tumor control mice). CP treatment caused abnormally accumulated urea cycle metabolites and serotonin metabolite hippuric acid in renal tissues that were not seen with DET alone or in combination with CP.

CONCLUSION

The CP and DET combination may be an effective intervention for melanoma with reduced side effects.

Impacts of methamphetamine and ketamine on C.elegans's physiological functions at environmentally relevant concentrations and eco-risk assessment in surface waters

In this work, C. elegans as a model organism was treated with methamphetamine (METH) and ketamine (KET) to assess its eco-toxicity at a range (0.05-250 μg L^-1) that covers environmentally relevant concentrations (0.05-0.5 μg L^-1). METH (≥0.05 μg L^-1) and KET (≥0.5 μg L^-1) significantly affected the feeding rate, locomotion, gustation and olfaction (P < 0.05), which may result in pronounced disturbance to aquatic ecology. Alterations in the contents of neurotransmitters (i.e., octopamine (OA), dopamine (DA), and serotonin (5-HT)) correlated with the physiology change. The metabolic activities and the antioxidase activity (i.e., superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)) of METH and KET in C. elegans were different, which could partly explain the difference of the physiological changes induced by the two substances. Moreover, these two drugs could induce vulva deformity, and the 50% effect concentrations were 620.34 μg L^-1 for METH and 54.39 μg L^-1 for KET, respectively. The risk quotients (RQ) in two Chinese rivers, the Shenzhen and Liangshui River, were calculated to assess eco-risks of METH and KET. RQs of KET in the Shenzhen River were over 0.1 at the medium risk level, indicating that eco-risks of illicit drugs to aquatic organism cannot be overlooked.

Role of biomarker tests for diagnosis of neuroendocrine tumours

Neuroendocrine tumours (NETs) are neoplasms that arise from neuroendocrine cells. Neuroendocrine cells and their tumours can secrete a wide range of amines and polypeptide hormones into the systemic circulation. This feature has triggered widespread investigation into circulating biomarkers for the diagnosis of NETs as well as for the prediction of the biological behaviour of tumour cells. Classic examples of circulating biomarkers for gastroenteropancreatic NETs include chromogranin A, neuron-specific enolase and pancreatic polypeptide as well as hormones that elicit clinical syndromes, such as serotonin and its metabolites, insulin, glucagon and gastrin. Biomarker metrics of general markers for diagnosing all gastroenteropancreatic NET subtypes are limited, but specific hormonal measurements can be of diagnostic value in select cases. In the past decade, methods for detecting circulating transcripts and tumour cells have been developed to improve the diagnosis of patients with NETs. Concurrently, modern scanning techniques and superior radiotracers for functional imaging have markedly expanded the options for clinicians dealing with NETs. Here, we review the latest research on biomarkers in the NET field to provide clinicians with a comprehensive overview of relevant diagnostic biomarkers that can be implemented in dedicated situations.

BIOCHEMICAL RESPONSES IN SYMPTOMATIC AND ASYMPTOMATIC PATIENTS WITH NEUROENDOCRINE TUMORS: POOLED ANALYSIS OF 2 PHASE 3 TRIALS

OBJECTIVE

Neuroendocrine tumors (NETs) are associated with elevated 5-hydroxyindoleacetic acid (5-HIAA) and chromogranin A (CgA) levels. This study aimed to analyze relationships between urinary 5-HIAA and plasma CgA levels and clinical outcomes.

METHODS

Centrally assessed biomarker levels and correlations with progression-free survival (PFS) and carcinoid syndrome (CS) symptom control were evaluated in a pooled analysis of CLARINET (96-week randomized, double-blind, placebo-controlled) and ELECT (16-week randomized, double-blind, placebo-controlled, 32-week initial open label and ≥2 year long-term extension open label) studies of adults with NETs, with (ELECT) or without (CLARINET) CS at 97 institutions. Patients were treated with subcutaneous lanreotide depot 120 mg monthly.

RESULTS

Of 319 pooled patients, 86% and 95% had baseline 5-HIAA and CgA data, respectively, with 47% and 74% having levels greater than the upper limit of normal (ULN). PFS was longer among patients who experienced a decrease in biomarker levels at week 12, with statistical significance reached in the CgA cohort (not reached vs. 14.4 months; P<.0001). A large proportion (87%) of patients without symptoms of CS in the CLARINET study had detectable levels of 5-HIAA (48% >ULN). In ELECT, patients with CS who received lanreotide and experienced a biochemical response (≥50% decrease from baseline) achieved greater symptom control.

CONCLUSION

This pooled analysis of two randomized, placebo-controlled trials demonstrated that 5-HIAA and CgA are secreted as biochemical biomarkers in many patients with NETs, regardless of clinical syndromes. Significant biochemical response was associated with improved clinical outcomes, as measured by improved PFS or improved CS symptom control.

ABBREVIATIONS

5-HIAA = 5-hydroxyindoleacetic acid; CgA = chromogranin A; CI = confidence interval; CLARINET = Controlled Study of Lanreotide Antiproliferative Response in Neuroendocrine Tumors; CS = carcinoid syndrome; ELECT = Evaluation of Lanreotide Depot/Autogel Efficacy and Safety as a Carcinoid Syndrome Treatment; HR = hazard ratio; ITT = intention-to-treat; NET = neuroendocrine tumor; PanNET = pancreatic NET; PFS = progression-free survival; PPI = proton pump inhibitor; SSA = somatostatin analogue; ULN = upper limit of normal.

Two Cases of Primary Hepatic Neuroendocrine Tumors and a Review of the Current Literature

Neuroendocrine tumors comprise approximately 1-2% of all gastrointestinal tumors, and while the liver is the most common site for metastasis of these tumors, primary hepatic neuroendocrine tumors are very rare entities. Since first being reported in 1958, there have been less than 150 cases reported in the literature. Because of the infrequent occurrence of these tumors, the pool of data available for analysis regarding these tumors is small. As such, the medical community must rely on the publication of case report data to further enlarge this data pool, with the hopes of eventually having enough data to draw meaningful, statistically significant conclusions with regard to diagnosis and management of these rare tumors. We have encountered two patients at our institution within the last year with primary hepatic neuroendocrine tumors. We present their cases in this manuscript in an effort to contribute to the available data on the disease. We also provide a concise review of the literature available to date regarding primary hepatic neuroendocrine tumors.

Proactive multi-modality treatment of Pancreatic Neuroendocrine Tumours (PNETs): Potential survival benefits

BACKGROUND/OBJECTIVES

Primary and metastatic pancreatic neuroendocrine tumours (PNET) can be treated with combination of surgery, locoregional and systemic therapy. Survival benefits from individual treatments have been well reported, however, the combined outcome from multimodal treatments are not well described in the literature. We report outcomes in a cohort of PNET patients treated with proactive, multimodality therapy.

METHODS

106 patients were identified from a single tertiary referral centre prospective database. Outcomes of treatment were studied, with the primary end point being death from any cause.

RESULTS

Median follow-up was 71 months and overall 5-year survival of 62%. In patients with stage I-III disease (51 patients) estimated 5-year survival was 90%. Median survival in patients with stage IV disease was 51 months with an estimated 5-year survival of 40% in this group. A total of 80 patients (75%) had surgery of which 16% suffered complications requiring intervention. There was no perioperative mortality.

CONCLUSIONS

This study demonstrates that proactive multimodal treatment is safe and may confer a survival benefit to patients in this cohort compared to historical data.

Telotristat ethyl in carcinoid syndrome: safety and efficacy in the TELECAST phase 3 trial

Telotristat ethyl, a tryptophan hydroxylase inhibitor, was efficacious and well tolerated in the phase 3 TELESTAR study in patients with carcinoid syndrome (CS) experiencing ≥4 bowel movements per day (BMs/day) while on somatostatin analogs (SSAs). TELECAST, a phase 3 companion study, assessed the safety and efficacy of telotristat ethyl in patients with CS (diarrhea, flushing, abdominal pain, nausea or elevated urinary 5-hydroxyindoleacetic acid (u5-HIAA)) with <4 BMs/day on SSAs (or ≥1 symptom or ≥4 BMs/day if not on SSAs) during a 12-week double-blind treatment period followed by a 36-week open-label extension (OLE). The primary safety and efficacy endpoints were incidence of treatment-emergent adverse events (TEAEs) and percent change from baseline in 24-h u5-HIAA at week 12. Patients (N = 76) were randomly assigned (1:1:1) to receive placebo or telotristat ethyl 250 mg or 500 mg 3 times per day (tid); 67 continued receiving telotristat ethyl 500 mg tid during the OLE. Through week 12, TEAEs were generally mild to moderate in severity; 5 (placebo), 1 (telotristat ethyl 250 mg) and 3 (telotristat ethyl 500 mg) patients experienced serious events, and the rate of TEAEs in the OLE was comparable. At week 12, significant reductions in u5-HIAA from baseline were observed, with Hodges-Lehmann estimators of median treatment differences from placebo of -54.0% (95% confidence limits, -85.0%, -25.1%, P < 0.001) and -89.7% (95% confidence limits, -113.1%, -63.9%, P < 0.001) for telotristat ethyl 250 mg and 500 mg. These results support the safety and efficacy of telotristat ethyl when added to SSAs in patients with CS diarrhea (ClinicalTrials.gov identifier: Nbib2063659).

Carcinoid-syndrome: recent advances, current status and controversies

PURPOSE OF REVIEW

To review recent advances and controversies in all aspects of carcinoid-syndrome.

RECENT FINDINGS

Over the last few years there have been a number of advances in all aspects of carcinoid syndrome as well as new therapies. These include new studies on its epidemiology which demonstrate it is increasing in frequency; increasing insights into the pathogenesis of its various clinical manifestations and into its natural history: definition of prognostic factors; new methods to verify its presence; the development of new drugs to treat its various manifestations, both initially and in somatostatin-refractory cases; and an increased understanding of the pathogenesis, natural history and management of carcinoid heart disease. These advances have generated several controversies and these are also reviewed.

SUMMARY

There have been numerous advances in all aspects of the carcinoid-syndrome, which is the most common functional syndrome neuroendocrine tumors produce. These advances are leading to new approaches to the management of these patients and in some cases to new controversies.

Management of neuroendocrine tumors of unknown primary

Neuroendocrine neoplams (NENs) are mostly relatively indolent malignancies but a significant number have metastatic disease at diagnosis mainly to the liver. Although in the majority of such cases the primary origin of the tumor can be identified, in approximately 11-22% no primary tumor is found and such cases are designated as NENs of unknown primary origin (UPO). This has significant therapeutic implications with respect to potentially resectable hepatic disease and/or application of appropriate medical therapy, either chemotherapeutic agents or targeted treatment, as the response to various treatments varies according to the origin of the primary tumor. This lack of tumor specific orientated treatment may also account for the relatively poorer prognosis of NENs of UPO compared to metastatic NENs with a known primary site. In the majority of cases the primary tumors are located in the small bowel and the lung, but a number may still elude detection. Occasionally the presence of a functional syndrome may direct to the specific tissue of origin but in the majority of cases a number of biochemical, imaging, histopathological and molecular modalities are utilized to help identify the primary origin of the tumor and direct treatment accordingly. Several diagnostic algorithms have recently been developed to help localize an occult primary tumor; however, in a number of cases no lesion is identified even after prolonged follow-up. It is expected that the delineation of the molecular signature of the different NENs may help identify such cases and provide appropriate treatment.

Hormone secreting gastro-entero-pancreatic neuroendocrine neoplasias (GEP-NEN): When to consider, how to diagnose?

Neuroendocrine neoplasms of the digestive system (GEP-NEN) represent a heterogeneous group of malignancies with various clinical presentation and prognosis. GEP-NENs can potentially affect all organs of the gastrointestinal tract; characteristically they share the biological property to produce and secrete peptides and neuroamines. About 30% of GEP-NENs are hormonally active and can cause specific clinical syndromes. The clinical presentation mainly depends on the primary site of the tumor and its functionality. Because of the wide spectrum of clinical symptoms and their misperceived rarity, diagnosis of GEP-NENs is often delayed for years and tumors are detected first in an advanced stage. Early identification of a specific hormonal syndrome can significantly impact tumor diagnosis and treatment, moreover the preoperative management of NEN hormonal release avoids potential life threatening hormonal crisis. However, GEP-NEN diagnostic work-up is challenging, it requires a multidisciplinary team and needs particular experience; standardized protocols and clinical experience are essential for a proper endocrine diagnostic work-up. In addition to the biochemical diagnostic, further radiologic and endoscopic imaging modalities are required moreover, somatostatin-receptor based functional imaging, using either Octreotide-scintigraphy or novel PET-based techniques with specific isotopes like Ga⁶⁸-DOTA-octreotate, plays an important role for the detection of the primary tumor as well as for the evaluation of the tumor extent.

MANAGEMENT OF ENDOCRINE DISEASE: Flushing: current concepts

OBJECTIVE

Flushing can be defined as a sensation of warmth accompanied by erythema that most commonly is seen on the face and which occurs in episodic attacks. Such a problem can be clinically problematic, since many conditions and drugs can be related to flushing, and while often there appears to be no underlying organic disease, it is important to exclude disorders since they may be life-threatening conditions.

DESIGN AND METHODS

We performed a search in MEDLINE using the terms 'flushing' in combination with 'carcinoid syndrome', 'pheochromocytoma', 'mastocytosis', 'menopausal hot flush' and 'treatment'. European and American guidelines relating to neuroendocrine tumours, mastocytosis and menopause were reviewed.

RESULTS

In this review, we discuss the main causes of flushing and propose an algorithm based on pathogenesis, which can be used to guide the clinical evaluation process. We also review recent significant developments in the assessment and treatment of the carcinoid syndrome and menopausal hot flushes, which should guide the clinical practice regarding this common but sometimes confusing condition.

CONCLUSIONS

When evaluating flushing, a precise systematic approach is needed to exclude potentially serious underlying causes, although despite this, the cause of the disorder is not always found. If symptoms are not progressive, the patient should be advised about its apparently benign nature in order to avoid unnecessary studies or initiating treatments of minimal benefit.

Biochemical Testing in Neuroendocrine Tumors

Neuroendocrine cells are widely distributed throughout the body. They can produce, store, and secrete peptides and biogenic amines. Neuroendocrine tumors (NETs) are rare, but most are found in the intestine, pancreas, and lung. NETs may cause specific hormonal symptoms (eg, carcinoid syndrome) or appear nonfunctional. Blood or urine concentrations of tumor-secreted amines and peptides have been used as biomarkers in the diagnosis and management of NETs. This article focuses on currently available biochemical testing of blood or urine for gastroenteropancreatic and lung NETs and discusses the limitations of these tests and the potential role of newer multianalyte markers for NET management.

Effect of hormone secretory syndromes on neuroendocrine tumor prognosis

The treatment of hormone hypersecretory syndromes caused by neuroendocrine tumors (NETs) can be a major challenge. NETs originating from the small intestine often secrete serotonin causing flushing, diarrhea and valve fibrosis, leading to dehydration or heart failure in severe cases. NETs from the pancreas can secrete a wider variety of hormones, like insulin, glucagon and gastrin leading to distinct clinical syndromes. Historically mortality in patients with functioning NETs was high due to the complications caused by the hypersecretion of hormones. This has been reduced with several drugs: proton-pump inhibitors decrease acid secretion caused by gastrinomas. Somatostatin analogs can inhibit the secretion of multiple hormones and these are now the cornerstone for treating patients with a gastroenteropancreatic NET. However, peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogs and everolimus can also decrease symptoms of hypersecretion and increase progression-free survival. Several factors affect the survival in patients with a functioning NET. Complications of hypersecretion negatively impact survival; however, secretion of hormones is also often a sign of a well-differentiated NET and due to the symptoms, functioning NETs can be detected in an earlier stage suggesting a positive effect on prognosis. The effect on survival is also dependent on the type of hormone being secreted. This review aims to study the effect of hormone secretion on the prognosis of NETs with the contemporary treatments options available today.

The North American Neuroendocrine Tumor Society Consensus Guidelines for Surveillance and Medical Management of Midgut Neuroendocrine Tumors

There have been significant developments in diagnostic and therapeutic options for patients with neuroendocrine tumors (NETs). Key phase 3 studies include the CLARINET trial, which evaluated lanreotide in patients with nonfunctioning enteropancreatic NETs; the RADIANT-2 and RADIANT-4 studies, which evaluated everolimus in functioning and nonfunctioning NETs of the gastrointestinal tract and lungs; the TELESTAR study, which evaluated telotristat ethyl in patients with refractory carcinoid syndrome; and the NETTER-1 trial, which evaluated Lu-DOTATATE in NETs of the small intestine and proximal colon (midgut). Based on these and other advances, the North American Neuroendocrine Tumor Society convened a multidisciplinary panel of experts with the goal of updating consensus-based guidelines for evaluation and treatment of midgut NETs. The medical aspects of these guidelines (focusing on systemic treatment, nonsurgical liver-directed therapy, and postoperative surveillance) are summarized in this article. Surgical guidelines are described in a companion article.

Diagnosing and Managing Carcinoid Heart Disease in Patients With Neuroendocrine Tumors: An Expert Statement

Carcinoid heart disease is a frequent occurrence in patients with carcinoid syndrome and is responsible for substantial morbidity and mortality. The pathophysiology of carcinoid heart disease is poorly understood; however, chronic exposure to excessive circulating serotonin is considered one of the most important contributing factors. Despite recognition, international consensus guidelines specifically addressing the diagnosis and management of carcinoid heart disease are lacking. Furthermore, there is considerable variation in multiple aspects of screening and management of the disease. The aim of these guidelines was to provide succinct, practical advice on the diagnosis and management of carcinoid heart disease as well as its surveillance. Recommendations and proposed algorithms for the investigation, screening, and management have been developed based on an evidence-based review of the published data and on the expert opinion of a multidisciplinary consensus panel consisting of neuroendocrine tumor experts, including oncologists, gastroenterologists, and endocrinologists, in conjunction with cardiologists and cardiothoracic surgeons.

Serotonin and poor neonatal adaptation after antidepressant exposure in utero

OBJECTIVE

Infants exposed to selective antidepressants (SADs) in utero are at risk to develop poor neonatal adaptation (PNA) postpartum. As symptoms are non-specific and the aetiology of PNA is unknown, the diagnostic process is hampered. We hypothesised that the serotonin metabolism plays a role in the aetiology of PNA.

METHODS

In this controlled study, infants admitted postpartum from February 2012 to August 2013 were included and followed for 3 days. Infants exposed to SADs during at least the last 2 weeks of fetal life were included in the patient group (n=63). Infants not exposed to psychotropic medication and admitted postpartum for another reason were included in the control group (n=126). The neonatal urinary 5-hydroxyindoleacetid acid (5-HIAA) levels of SAD-exposed infants who developed PNA, SAD-exposed infants who did not develop PNA and control infants were compared.

RESULTS

The course of the 5-HIAA levels over the first 3 days postpartum differed between infants with and without PNA (p≤0.001) with higher 5-HIAA levels in infants with PNA on day 1 (2.42 mmol/mol, p=0.001). Presence of maternal psychological distress modified this relationship.

CONCLUSIONS

A transient disturbance of the neonatal serotonergic system may play a role in the aetiology of PNA. Other factors, including the presence of maternal psychological distress, also seem to play a role.

Telotristat Ethyl, a Tryptophan Hydroxylase Inhibitor for the Treatment of Carcinoid Syndrome

Purpose

Preliminary studies suggested that telotristat ethyl, a tryptophan hydroxylase inhibitor, reduces bowel movement (BM) frequency in patients with carcinoid syndrome. This placebo-controlled phase III study evaluated telotristat ethyl in this setting.

Patients and Methods

Patients (N = 135) experiencing four or more BMs per day despite stable-dose somatostatin analog therapy received (1:1:1) placebo, telotristat ethyl 250 mg, or telotristat ethyl 500 mg three times per day orally during a 12-week double-blind treatment period. The primary end point was change from baseline in BM frequency. In an open-label extension, 115 patients subsequently received telotristat ethyl 500 mg.

Results

Estimated differences in BM frequency per day versus placebo averaged over 12 weeks were –0.81 for telotristat ethyl 250 mg ( P < .001) and ‒0.69 for telotristat ethyl 500 mg ( P < .001). At week 12, mean BM frequency reductions per day for placebo, telotristat ethyl 250 mg, and telotristat ethyl 500 mg were –0.9, –1.7, and –2.1, respectively. Responses, predefined as a BM frequency reduction ≥ 30% from baseline for ≥ 50% of the double-blind treatment period, were observed in 20%, 44%, and 42% of patients given placebo, telotristat ethyl 250 mg, and telotristat ethyl 500 mg, respectively. Both telotristat ethyl dosages significantly reduced mean urinary 5-hydroxyindole acetic acid versus placebo at week 12 ( P < .001). Mild nausea and asymptomatic increases in gamma-glutamyl transferase were observed in some patients receiving telotristat ethyl. Follow-up of patients during the open-label extension revealed no new safety signals and suggested sustained BM responses to treatment.

Conclusion

Among patients with carcinoid syndrome not adequately controlled by somatostatin analogs, treatment with telotristat ethyl was generally safe and well tolerated and resulted in significant reductions in BM frequency and urinary 5-hydroxyindole acetic acid.

Limited value for urinary 5-HIAA excretion as prognostic marker in gastrointestinal neuroendocrine tumours

OBJECTIVE

To determine if urinary 5-hydroxyindoleacetic acid (5-HIAA) excretion is of prognostic value for overall survival (OS) in patients with a gastrointestinal neuroendocrine tumour (NET) and to compare the prognostic value with patient characteristics, ENETS/WHO grading, ENETS TNM staging and biomarkers.

DESIGN AND METHODS

Data was collected from patients with a gastrointestinal NET or a NET with gastrointestinal metastases and available 5-HIAA excretion in 24-h urine samples. Laboratory results were stratified for urinary 5-HIAA and chromogranin A (CgA): <2× upper limit of normal (ULN), 2-10× ULN, or >10× ULN. For neuron-specific enolase (NSE), this was the reference range or >1× ULN. OS was compared using Kaplan-Meier and log-rank tests, and hazard ratios were calculated using Cox regression for univariate and multivariate analyses.

RESULTS

A total of 371 patients were included, 46.6% female with a mean age of 59.9 years. OS was shortest in patients with urinary 5-HIAA excretion >10× ULN vs reference range (median 83 months vs 141 months, P = 0.002). In univariate analysis, urinary 5-HIAA excretion >10× ULN was a negative predictor (HR 1.62, 95% CI: 1.09-2.39). However, in multivariate analysis, only age (HR 1.04, 95% CI: 1.01-1.08), grade 3 disease (HR 5.09, 95% CI: 2.20-11.79), NSE >1× ULN (HR 2.36, 95% CI: 1.34-4.14) and CgA >10× ULN (HR 3.61, 95% CI: 1.56-8.34) remained as the predictors.

CONCLUSION

Urinary 5-HIAA excretion >10× ULN is a negative predictor for OS. However, when added to other biomarkers and grading, it is no longer a predictor for OS. Therefore, it should only be determined to assess carcinoid syndrome and not for prognostic value.

Neuroendocrine tumours of the small bowel: interpretation of raised circulating chromogranin A, urinary 5 hydroxy indole acetic acid and circulating neurokinin A

BACKGROUND

Neuroendocrine tumours (NETs) of the small bowel are difficult to diagnose as symptoms are non-specific and more often found in common gastrointestinal diseases. Chromogranin A (CGA), urinary 5 hydroxy indole acetic acid (U-5HIAA) and Neurokinin A (NKA) are used as laboratory diagnostic tests but results may be misleading or confusing.

AIM

To clarify the relevance of NET biomarkers for diagnosis of small bowel NETs.

DESIGN

A review of laboratory test results.

METHODS

We reviewed 500 consecutive raised plasma CGA, U-5HIAA and plasma NKA, results from patients in N Ireland. The diagnosis of NET was confirmed by the Northern Ireland Cancer Registry.

RESULTS

In 500 specimens recording raised CGA, 52.2% were from patients with NETs, 13.6% being small bowel tumours, 5.4% of specimens from patients with auto-immune atrophic gastritis and 15.4% from patients taking proton pump inhibitors. In 500 specimens with raised U-5HIAA, 87.8% were from patients with NETs, 68.2% being small bowel tumours. Lung NETs contributed 12.2% and NETs from other sites, 7.4%. Of 500 specimens with raised NKA (reference range (RR) > 20 ng/L), 72.6% were from patients with small bowel NETs and 6% specimens from patients with other NETs. In 20% of specimens NKA concentrations were 21-23 ng/L, within limits of assay precision.

CONCLUSION

CGA remains the best general circulating marker for NETs although only half of raised test results are due to an NET. U-5HIAA is an excellent marker for small bowel and lung NETs with 80% of high test results confirming these diagnoses. NKA is the most specific biomarker for small bowel NETs.

Neuroendocrine tumor biomarkers: From monoanalytes to transcripts and algorithms

The management of neuroendocrine neoplasia remains a perplexing problem because of the lack of knowledge of the biology of the disease, its late presentation, the relative insensitivity of imaging modalities and a paucity of predictably effective treatment options. A critical limitation is posed by the lack of accurate biomarkers to guide management, monitor the efficacy of therapy and provide a prognostic assessment of disease progress. Currently utilized monoanalyte biomarkers (e.g. chromogranin, serotonin, pancreastatin etc.) exhibit variable metrics, poor sensitivity, specificity, and predictive ability and are rarely used to guide clinical decision making. A National Cancer Institute Neuroendocrine Tumor summit conference held in 2007 noted biomarker limitations to be a crucial unmet need in the management of neuroendocrine tumors. Nevertheless little progress has been made in this field until recently with the consideration of blood transcript analysis, circulating tumor cells and miRNA measurement. Given the complexity and multidimensionality of the neoplastic process itself, the heterogeneity of neuroendocrine tumors (NET) as well as the interaction of the tumor microenvironment, it is not unexpected that no single (monoanalyte) biomarker has proven to be effective. This deduction reflects the growing recognition that use of a monoanalyte to define a multidimensional disease process has inherent flaws. Logic dictates that no single measured parameter can capture the pathobiological diversity of neoplasia and monoanalytes cannot define the multiple variables (proliferation, metabolic activity, invasive potential and metastatic propensity) that constitute tumor growth. Thus far, most biomarkers whether in tissue or blood/urine have been single analytes with varying degrees of sensitivity and specificity and in general have failed to exhibit robust metrics or lacked methodological rigor. Neuroendocrine (NE) disease represents an area of biomarker paucity since the individual biomarkers (gastrin, insulin etc) are not widely applicable to the diverse types of NE neoplasia (NEN). Broad spectrum markers such as CgA have limitations in sensitivity, specificity and reproducibility. This review serves to provide a general background of the evolution of NET biomarkers. It provides an assessment of their current and past usage and limitations in assessing their diagnostic, pathologic and prognostic aspects in respect of NET. It provides a view of the changing methodology of biomarker development and the application of biomathematical analyses to redefining detection and treatment. Finally, it presents a description and consensus on current advances in transcript analysis, miRNA measurement and circulating tumor cell identification.

Clinical Presentation and Diagnosis of Neuroendocrine Tumors

Neuroendocrine tumors (NETs) are slow-growing neoplasms capable of storing and secreting different peptides and neuroamines. Some of these substances cause specific symptom complexes, whereas others are silent. They usually have episodic expression, and the diagnosis is often made at a late stage. Although considered rare, the incidence of NETs is increasing. For these reasons, a high index of suspicion is needed. In this article, the different clinical syndromes and the pathophysiology of each tumor as well as the new and emerging biochemical markers and imaging techniques that should be used to facilitate an early diagnosis, follow-up, and prognosis are reviewed.

Serum and plasma 5-hydroxyindoleacetic acid as an alternative to 24-h urine 5-hydroxyindoleacetic acid measurement

BACKGROUND

Neuroendocrine tumours are slow growing tumours known to secrete a variety of vasoactive peptides which give rise to symptoms of the carcinoid syndrome. The diagnosis and monitoring of patients with neuroendocrine tumours is undertaken in many centres using 24 h urinary measurement of 5-hydroxyindoleacetic acid. However, 5-hydroxyindoleacetic acid can also be quantified in plasma and serum.

METHODS

We measured 5-hydroxyindoleacetic acid concentration in 134 paired EDTA plasma and urine samples from 108 patients with known neuroendocrine tumours and 26 healthy volunteers. We also compared 5-hydroxyindoleacetic acid concentrations in paired serum and plasma samples (n = 63), then analysed paired urine and serum samples (n = 97). Furthermore, we examined the impact of renal impairment on serum 5-hydroxyindoleacetic acid by analysing 5-hydroxyindoleacetic acid in patients without neuroendocrine tumours in different stages of chronic kidney disease, as indicated by the estimated glomerular filtration rate.

RESULTS

Plasma and urine 5-hydroxyindoleacetic acid had very similar diagnostic sensitivities and specificities, with areas under the curve on ROC analysis of 0.917 and 0.920, respectively. Serum and plasma 5-hydroxyindoleacetic acid values showed good correlation but serum results demonstrated a positive bias, indicating the necessity for different serum and plasma reference intervals. There was an inverse correlation between estimated glomerular filtration rate and serum 5-hydroxyindoleacetic acid concentration, with 5-hydroxyindoleacetic acid increasing once the estimated glomerular filtration rate falls below 60 mL/min/1.73 m(2).

CONCLUSION

The measurement of both serum and plasma 5-hydroxyindoleacetic acid can be used for the diagnosis and monitoring of patients with neuroendocrine tumours. Provided renal function is taken into consideration, either of these tests should be incorporated into standard practice as an alternative assay to urinary 5-hydroxyindoleacetic acid.

Circulating tumor markers in patients with neuroendocrine tumors – a clinical perspective

Abstract: 

Neuroendocrine tumors (NETs) are uncommon malignancies with a very diverse presentation and prognosis. Patients with NETs frequently have circulating tumor biomarkers that may aid in the diagnosis and help with prognostication. The most commonly used and best studied marker is chromogranin A, which appears to reflect the tumor burden and is useful at the time of diagnosis, and to monitor for recurrence after resection as well as to assess response to systemic therapy. Despite being the best studied marker, chromogranin A has significant limitations. Multiple other biomarkers are in use, but most have not been studied well and need further validation before being recommended for clinical practice. We review both established and novel circulating biomarkers, and highlight some of the limitations of tumor marker use in patients with NETs.

Liquid chromatography tandem mass spectrometry in the clinical laboratory

Clinical laboratory medicine has seen the introduction and evolution of liquid chromatography tandem mass spectrometry in routine clinical laboratories over the last 10–15 years. There still exists a wide diversity of assays from very esoteric and highly specialist manual assays to more simplified kit-based assays. The technology is not static as manufacturers are continually making improvements. Mass spectrometry is now commonly used in several areas of diagnostics including therapeutic drug monitoring, toxicology, endocrinology, paediatrics and microbiology. Some of the most high throughput analyses or common analytes include vitamin D, immunosuppressant monitoring, androgen measurement and newborn screening. It also offers flexibility for the measurement of analytes in a variety of different matrices which would prove difficult with immunoassays. Unlike immunoassays or high-pressure liquid chromatography assays using ultraviolet or fluorescence detection, mass spectrometry offers better specificity and reduced interferences if attention is paid to potential isobaric compounds. Furthermore, multiplexing, which enables multiple analytes to be measured with the same volume of serum is advantageous, and the requirement for large sample volumes is decreasing as instrument sensitivity increases. There are many emerging applications in the literature. Using mass spectrometry to identify novel isoforms or modified peptides is possible as is quantification of proteins and peptides, with or without protein digests. Future developments by the manufacturers may also include mechanisms to improve the throughput of samples and strategies to decrease the level of skill required by the operators.

Serial surveillance of carcinoid heart disease: factors associated with echocardiographic progression and mortality

Background:

Carcinoid heart disease is a complication of metastatic neuroendocrine tumours (NETs). We sought to identify factors associated with echocardiographic progression of carcinoid heart disease and death in patients with metastatic NETs.

Methods:

Patients with advanced non-pancreatic NETs and documented liver metastases and/or carcinoid syndrome underwent prospective serial clinical, biochemical, echocardiographic and radiological assessment. Patients were categorised as carcinoid heart disease progressors, non-progressors or deceased. Multinomial regression was used to assess the univariate association between variables and carcinoid heart disease progression.

Results:

One hundred and thirty-seven patients were included. Thirteen patients (9%) were progressors, 95 (69%) non-progressors and 29 (21%) patients deceased. Baseline median levels of serum N-terminal pro-brain natriuretic peptide (NT-proBNP) and plasma 5-hydroxyindoleacetic acid (5-HIAA) were significantly higher in the progressors. Every 100 nmol l⁻¹ increase in 5-HIAA yielded a 5% greater odds of disease progression (OR 1.05, 95% CI: 1.01, 1.09; P=0.012) and a 7% greater odds of death (OR 1.07, 95% CI: 1.03, 1.10; P=0.001). A 100 ng l⁻¹ increase in NT-proBNP did not increase the risk of progression, but did increase the risk of death by 11%.

Conclusions:

The biochemical burden of disease, in particular baseline plasma 5-HIAA concentration, is independently associated with carcinoid heart disease progression and death. Clinical and radiological factors are less useful prognostic indicators of carcinoid heart disease progression and/or death.